It had actually been working fine in 20.04 until a recent kernel update to 5.4.0-33.37.

Since the update, it always fails with this stack trace:

[140594.217061] ------------[ cut here ]------------
[140594.217062] sysfs group 'power' not found for kobject 'i2c-11'
[140594.217079] WARNING: CPU: 5 PID: 64631 at fs/sysfs/group.c:279 sysfs_remove_group+0x7c/0x80
[140594.217080] Modules linked in: vboxnetadp(OE) vboxnetflt(OE) vboxdrv(OE) binfmt_misc ccm rfcomm cmac algif_hash algif_skcipher af_alg cdc_ether usbnet r8152 mii snd_usb_audio snd_usbmidi_lib bnep bonding btusb btrtl btbcm btintel bluetooth ecdh_generic ecc evdi(OE) aufs uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_common overlay nls_iso8859_1 snd_hda_codec_conexant snd_hda_codec_generic ledtrig_audio snd_hda_codec_hdmi snd_hda_intel snd_intel_dspcfg snd_hda_codec snd_hda_core snd_hwdep snd_pcm snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq snd_seq_device snd_timer snd iwlmvm edac_mce_amd mac80211 kvm_amd ccp soundcore libarc4 kvm iwlwifi input_leds joydev serio_raw hp_wmi sparse_keymap ipmi_devintf wmi_bmof hid_multitouch k10temp cfg80211 ipmi_msghandler ucsi_acpi typec_ucsi typec hp_wireless mac_hid sch_fq_codel v4l2loopback(OE) videodev mc parport_pc ppdev lp parport ip_tables x_tables autofs4 uas usb_storage raid10 raid456 async_raid6_recov async_memcpy
[140594.217138]  async_pq async_xor async_tx xor usbhid raid6_pq libcrc32c raid1 raid0 multipath linear crct10dif_pclmul crc32_pclmul hid_generic ghash_clmulni_intel amdgpu amd_iommu_v2 gpu_sched i2c_algo_bit ttm nvme aesni_intel drm_kms_helper syscopyarea sysfillrect crypto_simd sysimgblt i2c_hid fb_sys_fops hid ahci psmouse drm cryptd libahci i2c_piix4 glue_helper nvme_core r8169 realtek wmi video i2c_amd_mp2_plat i2c_amd_mp2_pci
[140594.217167] CPU: 5 PID: 64631 Comm: kworker/5:0 Tainted: G           OE     5.4.0-33-generic #37-Ubuntu
[140594.217169] Hardware name: HP HP EliteBook 755 G5/83D5, BIOS Q81 Ver. 01.10.00 01/03/2020
[140594.217183] Workqueue: events drm_dp_destroy_connector_work [drm_kms_helper]
[140594.217187] RIP: 0010:sysfs_remove_group+0x7c/0x80
[140594.217191] Code: e7 e8 98 b9 ff ff 5b 41 5c 41 5d 5d c3 4c 89 e7 e8 e9 b4 ff ff eb c9 49 8b 55 00 48 8b 33 48 c7 c7 40 d4 58 a5 e8 4f 90 d1 ff <0f> 0b eb d8 0f 1f 44 00 00 48 85 f6 74 37 55 48 89 e5 41 55 41 54
[140594.217192] RSP: 0018:ffffb1ea82f3fc00 EFLAGS: 00010286
[140594.217194] RAX: 0000000000000000 RBX: ffffffffa52f3b60 RCX: 0000000000000006
[140594.217196] RDX: 0000000000000007 RSI: 0000000000000096 RDI: ffff9085dfd578c0
[140594.217197] RBP: ffffb1ea82f3fc18 R08: 0000000000000851 R09: 0000000000000004
[140594.217198] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
[140594.217199] R13: ffff9082e1c93800 R14: ffffffffc0327140 R15: ffffffffc0327140
[140594.217201] FS:  0000000000000000(0000) GS:ffff9085dfd40000(0000) knlGS:0000000000000000
[140594.217202] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[140594.217204] CR2: 00007f81ed808000 CR3: 000000041687e000 CR4: 00000000003406a0
[140594.217205] Call Trace:
[140594.217213]  dpm_sysfs_remove+0x59/0x60
[140594.217217]  device_del+0x85/0x370
[140594.217220]  ? class_find_device+0x97/0xf0
[140594.217223]  device_unregister+0x1b/0x60
[140594.217226]  device_destroy+0x4b/0x70
[140594.217229]  i2cdev_detach_adapter+0x58/0x90
[140594.217231]  i2cdev_notifier_call+0x21/0x40
[140594.217235]  notifier_call_chain+0x55/0x80
[140594.217238]  blocking_notifier_call_chain+0x50/0x70
[140594.217241]  device_del+0x7d/0x370
[140594.217244]  device_unregister+0x1b/0x60
[140594.217247]  i2c_del_adapter+0x238/0x300
[140594.217257]  drm_dp_port_teardown_pdt+0x1f/0x40 [drm_kms_helper]
[140594.217267]  drm_dp_destroy_connector_work+0xa3/0x110 [drm_kms_helper]
[140594.217271]  process_one_work+0x1eb/0x3b0
[140594.217274]  worker_thread+0x4d/0x400
[140594.217277]  kthread+0x104/0x140
[140594.217279]  ? process_one_work+0x3b0/0x3b0
[140594.217281]  ? kthread_park+0x90/0x90
[140594.217285]  ret_from_fork+0x22/0x40
[140594.217288] ---[ end trace 854f992547f30c28 ]---
[140594.217339] ------------[ cut here ]------------
[140594.217340] sysfs group 'power' not found for kobject 'i2c-11'
[140594.217352] WARNING: CPU: 5 PID: 64631 at fs/sysfs/group.c:279 sysfs_remove_group+0x7c/0x80
[140594.217352] Modules linked in: vboxnetadp(OE) vboxnetflt(OE) vboxdrv(OE) binfmt_misc ccm rfcomm cmac algif_hash algif_skcipher af_alg cdc_ether usbnet r8152 mii snd_usb_audio snd_usbmidi_lib bnep bonding btusb btrtl btbcm btintel bluetooth ecdh_generic ecc evdi(OE) aufs uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_common overlay nls_iso8859_1 snd_hda_codec_conexant snd_hda_codec_generic ledtrig_audio snd_hda_codec_hdmi snd_hda_intel snd_intel_dspcfg snd_hda_codec snd_hda_core snd_hwdep snd_pcm snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq snd_seq_device snd_timer snd iwlmvm edac_mce_amd mac80211 kvm_amd ccp soundcore libarc4 kvm iwlwifi input_leds joydev serio_raw hp_wmi sparse_keymap ipmi_devintf wmi_bmof hid_multitouch k10temp cfg80211 ipmi_msghandler ucsi_acpi typec_ucsi typec hp_wireless mac_hid sch_fq_codel v4l2loopback(OE) videodev mc parport_pc ppdev lp parport ip_tables x_tables autofs4 uas usb_storage raid10 raid456 async_raid6_recov async_memcpy
[140594.217385]  async_pq async_xor async_tx xor usbhid raid6_pq libcrc32c raid1 raid0 multipath linear crct10dif_pclmul crc32_pclmul hid_generic ghash_clmulni_intel amdgpu amd_iommu_v2 gpu_sched i2c_algo_bit ttm nvme aesni_intel drm_kms_helper syscopyarea sysfillrect crypto_simd sysimgblt i2c_hid fb_sys_fops hid ahci psmouse drm cryptd libahci i2c_piix4 glue_helper nvme_core r8169 realtek wmi video i2c_amd_mp2_plat i2c_amd_mp2_pci
[140594.217402] CPU: 5 PID: 64631 Comm: kworker/5:0 Tainted: G        W  OE     5.4.0-33-generic #37-Ubuntu
[140594.217403] Hardware name: HP HP EliteBook 755 G5/83D5, BIOS Q81 Ver. 01.10.00 01/03/2020
[140594.217413] Workqueue: events drm_dp_destroy_connector_work [drm_kms_helper]
[140594.217416] RIP: 0010:sysfs_remove_group+0x7c/0x80
[140594.217419] Code: e7 e8 98 b9 ff ff 5b 41 5c 41 5d 5d c3 4c 89 e7 e8 e9 b4 ff ff eb c9 49 8b 55 00 48 8b 33 48 c7 c7 40 d4 58 a5 e8 4f 90 d1 ff <0f> 0b eb d8 0f 1f 44 00 00 48 85 f6 74 37 55 48 89 e5 41 55 41 54
[140594.217420] RSP: 0018:ffffb1ea82f3fd28 EFLAGS: 00010282
[140594.217421] RAX: 0000000000000000 RBX: ffffffffa52f3b60 RCX: 0000000000000006
[140594.217423] RDX: 0000000000000007 RSI: 0000000000000082 RDI: ffff9085dfd578c0
[140594.217424] RBP: ffffb1ea82f3fd40 R08: 000000000000087a R09: 0000000000000004
[140594.217425] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
[140594.217426] R13: ffff9083406808a8 R14: 0000000000000000 R15: dead000000000100
[140594.217427] FS:  0000000000000000(0000) GS:ffff9085dfd40000(0000) knlGS:0000000000000000
[140594.217429] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[140594.217430] CR2: 00007f81ed808000 CR3: 000000041687e000 CR4: 00000000003406a0
[140594.217431] Call Trace:
[140594.217435]  dpm_sysfs_remove+0x59/0x60
[140594.217437]  device_del+0x85/0x370
[140594.217440]  device_unregister+0x1b/0x60
[140594.217443]  i2c_del_adapter+0x238/0x300
[140594.217453]  drm_dp_port_teardown_pdt+0x1f/0x40 [drm_kms_helper]
[140594.217462]  drm_dp_destroy_connector_work+0xa3/0x110 [drm_kms_helper]
[140594.217465]  process_one_work+0x1eb/0x3b0
[140594.217468]  worker_thread+0x4d/0x400
[140594.217470]  kthread+0x104/0x140
[140594.217473]  ? process_one_work+0x3b0/0x3b0
[140594.217475]  ? kthread_park+0x90/0x90
[140594.217478]  ret_from_fork+0x22/0x40
[140594.217480] ---[ end trace 854f992547f30c29 ]---
[140594.217500] [drm] DM_MST: Disabling connector: 00000000b20c1ffc [id: 119] [master: 0000000071ae0507]
[140594.217614] ------------[ cut here ]------------
[140594.217615] sysfs group 'power' not found for kobject 'i2c-12'
[140594.217627] WARNING: CPU: 5 PID: 64631 at fs/sysfs/group.c:279 sysfs_remove_group+0x7c/0x80
[140594.217627] Modules linked in: vboxnetadp(OE) vboxnetflt(OE) vboxdrv(OE) binfmt_misc ccm rfcomm cmac algif_hash algif_skcipher af_alg cdc_ether usbnet r8152 mii snd_usb_audio snd_usbmidi_lib bnep bonding btusb btrtl btbcm btintel bluetooth ecdh_generic ecc evdi(OE) aufs uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_common overlay nls_iso8859_1 snd_hda_codec_conexant snd_hda_codec_generic ledtrig_audio snd_hda_codec_hdmi snd_hda_intel snd_intel_dspcfg snd_hda_codec snd_hda_core snd_hwdep snd_pcm snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq snd_seq_device snd_timer snd iwlmvm edac_mce_amd mac80211 kvm_amd ccp soundcore libarc4 kvm iwlwifi input_leds joydev serio_raw hp_wmi sparse_keymap ipmi_devintf wmi_bmof hid_multitouch k10temp cfg80211 ipmi_msghandler ucsi_acpi typec_ucsi typec hp_wireless mac_hid sch_fq_codel v4l2loopback(OE) videodev mc parport_pc ppdev lp parport ip_tables x_tables autofs4 uas usb_storage raid10 raid456 async_raid6_recov async_memcpy
[140594.217660]  async_pq async_xor async_tx xor usbhid raid6_pq libcrc32c raid1 raid0 multipath linear crct10dif_pclmul crc32_pclmul hid_generic ghash_clmulni_intel amdgpu amd_iommu_v2 gpu_sched i2c_algo_bit ttm nvme aesni_intel drm_kms_helper syscopyarea sysfillrect crypto_simd sysimgblt i2c_hid fb_sys_fops hid ahci psmouse drm cryptd libahci i2c_piix4 glue_helper nvme_core r8169 realtek wmi video i2c_amd_mp2_plat i2c_amd_mp2_pci
[140594.217677] CPU: 5 PID: 64631 Comm: kworker/5:0 Tainted: G        W  OE     5.4.0-33-generic #37-Ubuntu
[140594.217678] Hardware name: HP HP EliteBook 755 G5/83D5, BIOS Q81 Ver. 01.10.00 01/03/2020
[140594.217689] Workqueue: events drm_dp_destroy_connector_work [drm_kms_helper]
[140594.217692] RIP: 0010:sysfs_remove_group+0x7c/0x80
[140594.217694] Code: e7 e8 98 b9 ff ff 5b 41 5c 41 5d 5d c3 4c 89 e7 e8 e9 b4 ff ff eb c9 49 8b 55 00 48 8b 33 48 c7 c7 40 d4 58 a5 e8 4f 90 d1 ff <0f> 0b eb d8 0f 1f 44 00 00 48 85 f6 74 37 55 48 89 e5 41 55 41 54
[140594.217696] RSP: 0018:ffffb1ea82f3fc00 EFLAGS: 00010286
[140594.217697] RAX: 0000000000000000 RBX: ffffffffa52f3b60 RCX: 0000000000000006
[140594.217698] RDX: 0000000000000007 RSI: 0000000000000096 RDI: ffff9085dfd578c0
[140594.217699] RBP: ffffb1ea82f3fc18 R08: 000000000000089c R09: 0000000000000004
[140594.217700] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
[140594.217701] R13: ffff9082e1c92000 R14: ffffffffc0327140 R15: ffffffffc0327140
[140594.217703] FS:  0000000000000000(0000) GS:ffff9085dfd40000(0000) knlGS:0000000000000000
[140594.217704] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[140594.217706] CR2: 00007f81ed808000 CR3: 000000041687e000 CR4: 00000000003406a0
[140594.217707] Call Trace:
[140594.217711]  dpm_sysfs_remove+0x59/0x60
[140594.217713]  device_del+0x85/0x370
[140594.217716]  ? class_find_device+0x97/0xf0
[140594.217718]  device_unregister+0x1b/0x60
[140594.217721]  device_destroy+0x4b/0x70
[140594.217723]  i2cdev_detach_adapter+0x58/0x90
[140594.217725]  i2cdev_notifier_call+0x21/0x40
[140594.217728]  notifier_call_chain+0x55/0x80
[140594.217731]  blocking_notifier_call_chain+0x50/0x70
[140594.217733]  device_del+0x7d/0x370
[140594.217736]  device_unregister+0x1b/0x60
[140594.217738]  i2c_del_adapter+0x238/0x300
[140594.217748]  drm_dp_port_teardown_pdt+0x1f/0x40 [drm_kms_helper]
[140594.217757]  drm_dp_destroy_connector_work+0xa3/0x110 [drm_kms_helper]
[140594.217760]  process_one_work+0x1eb/0x3b0
[140594.217762]  worker_thread+0x4d/0x400
[140594.217765]  kthread+0x104/0x140
[140594.217767]  ? process_one_work+0x3b0/0x3b0
[140594.217769]  ? kthread_park+0x90/0x90
[140594.217772]  ret_from_fork+0x22/0x40
[140594.217775] ---[ end trace 854f992547f30c2a ]---
[140594.217814] ------------[ cut here ]------------
[140594.217815] sysfs group 'power' not found for kobject 'i2c-12'
[140594.217824] WARNING: CPU: 5 PID: 64631 at fs/sysfs/group.c:279 sysfs_remove_group+0x7c/0x80
[140594.217825] Modules linked in: vboxnetadp(OE) vboxnetflt(OE) vboxdrv(OE) binfmt_misc ccm rfcomm cmac algif_hash algif_skcipher af_alg cdc_ether usbnet r8152 mii snd_usb_audio snd_usbmidi_lib bnep bonding btusb btrtl btbcm btintel bluetooth ecdh_generic ecc evdi(OE) aufs uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_common overlay nls_iso8859_1 snd_hda_codec_conexant snd_hda_codec_generic ledtrig_audio snd_hda_codec_hdmi snd_hda_intel snd_intel_dspcfg snd_hda_codec snd_hda_core snd_hwdep snd_pcm snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq snd_seq_device snd_timer snd iwlmvm edac_mce_amd mac80211 kvm_amd ccp soundcore libarc4 kvm iwlwifi input_leds joydev serio_raw hp_wmi sparse_keymap ipmi_devintf wmi_bmof hid_multitouch k10temp cfg80211 ipmi_msghandler ucsi_acpi typec_ucsi typec hp_wireless mac_hid sch_fq_codel v4l2loopback(OE) videodev mc parport_pc ppdev lp parport ip_tables x_tables autofs4 uas usb_storage raid10 raid456 async_raid6_recov async_memcpy
[140594.217852]  async_pq async_xor async_tx xor usbhid raid6_pq libcrc32c raid1 raid0 multipath linear crct10dif_pclmul crc32_pclmul hid_generic ghash_clmulni_intel amdgpu amd_iommu_v2 gpu_sched i2c_algo_bit ttm nvme aesni_intel drm_kms_helper syscopyarea sysfillrect crypto_simd sysimgblt i2c_hid fb_sys_fops hid ahci psmouse drm cryptd libahci i2c_piix4 glue_helper nvme_core r8169 realtek wmi video i2c_amd_mp2_plat i2c_amd_mp2_pci
[140594.217867] CPU: 5 PID: 64631 Comm: kworker/5:0 Tainted: G        W  OE     5.4.0-33-generic #37-Ubuntu
[140594.217868] Hardware name: HP HP EliteBook 755 G5/83D5, BIOS Q81 Ver. 01.10.00 01/03/2020
[140594.217876] Workqueue: events drm_dp_destroy_connector_work [drm_kms_helper]
[140594.217879] RIP: 0010:sysfs_remove_group+0x7c/0x80
[140594.217881] Code: e7 e8 98 b9 ff ff 5b 41 5c 41 5d 5d c3 4c 89 e7 e8 e9 b4 ff ff eb c9 49 8b 55 00 48 8b 33 48 c7 c7 40 d4 58 a5 e8 4f 90 d1 ff <0f> 0b eb d8 0f 1f 44 00 00 48 85 f6 74 37 55 48 89 e5 41 55 41 54
[140594.217882] RSP: 0018:ffffb1ea82f3fd28 EFLAGS: 00010282
[140594.217883] RAX: 0000000000000000 RBX: ffffffffa52f3b60 RCX: 0000000000000006
[140594.217884] RDX: 0000000000000007 RSI: 0000000000000082 RDI: ffff9085dfd578c0
[140594.217885] RBP: ffffb1ea82f3fd40 R08: 00000000000008c5 R09: 0000000000000004
[140594.217886] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
[140594.217887] R13: ffff9083406840a8 R14: 0000000000000000 R15: dead000000000100
[140594.217888] FS:  0000000000000000(0000) GS:ffff9085dfd40000(0000) knlGS:0000000000000000
[140594.217889] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[140594.217890] CR2: 00007f81ed808000 CR3: 000000041687e000 CR4: 00000000003406a0
[140594.217891] Call Trace:
[140594.217894]  dpm_sysfs_remove+0x59/0x60
[140594.217896]  device_del+0x85/0x370
[140594.217899]  device_unregister+0x1b/0x60
[140594.217901]  i2c_del_adapter+0x238/0x300
[140594.217909]  drm_dp_port_teardown_pdt+0x1f/0x40 [drm_kms_helper]
[140594.217916]  drm_dp_destroy_connector_work+0xa3/0x110 [drm_kms_helper]
[140594.217920]  process_one_work+0x1eb/0x3b0
[140594.217922]  worker_thread+0x4d/0x400
[140594.217924]  kthread+0x104/0x140
[140594.217926]  ? process_one_work+0x3b0/0x3b0
[140594.217928]  ? kthread_park+0x90/0x90
[140594.217930]  ret_from_fork+0x22/0x40
[140594.217932] ---[ end trace 854f992547f30c2b ]---