I wish I could place a date on when the issues started. My guess is that it was either late May or early June. The issue happens quite frequently in the last updates and now I get sometimes a black screen on the laptop while the external monitor remains working. A restart of the system brings things back to work but the freezes quite happening maybe even more frequently now.

I will try the mainline kernel and report results. The list of kernels I had in the system as per your command is below.

I would say that version 5.4.0-29 was definitely working fine and that it was one of the 5.4.0-3x release that started the problem.

Aug 03 22:01:02 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-42-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Aug 01 06:52:50 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-42-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 29 09:48:41 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-42-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 26 10:15:00 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-42-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 24 13:44:02 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-42-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 23 08:11:18 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-42-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 21 08:15:04 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-42-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 15 17:41:07 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-40-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 14 08:33:03 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-40-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 11 13:24:59 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-40-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 10 07:46:22 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-40-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 08 08:04:09 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-40-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 05 12:58:30 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-40-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 03 08:41:41 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-40-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jul 02 16:08:33 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-39-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jun 26 10:49:52 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-39-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro modprobe.blacklist=nouveau
Jun 26 09:57:03 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-39-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro
Jun 25 21:53:56 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-39-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro
Jun 20 18:15:04 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-37-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro
Jun 18 11:35:43 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-37-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro
Jun 16 18:26:37 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_dd5xf4@/vmlinuz-5.4.0-37-generic root=ZFS=rpool/ROOT/ubuntu_dd5xf4 ro
Jun 15 16:43:07 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_x13bv2@autozsys_1kiv8w/vmlinuz-5.4.0-37-generic root=ZFS=rpool/ROOT/ubuntu_x13bv2@autozsys_1kiv8w ro
Jun 15 06:45:14 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_x13bv2@/vmlinuz-5.4.0-37-generic root=ZFS=rpool/ROOT/ubuntu_x13bv2 ro
Jun 12 14:25:05 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_w5d0b7@autozsys_x65hvt/vmlinuz-5.4.0-37-generic root=ZFS=rpool/ROOT/ubuntu_w5d0b7@autozsys_x65hvt ro
Jun 11 13:14:30 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_w5d0b7@/vmlinuz-5.4.0-37-generic root=ZFS=rpool/ROOT/ubuntu_w5d0b7 ro
Jun 08 21:27:44 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_w5d0b7@/vmlinuz-5.4.0-33-generic root=ZFS=rpool/ROOT/ubuntu_w5d0b7 ro
Jun 01 20:50:11 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_w5d0b7@/vmlinuz-5.4.0-33-generic root=ZFS=rpool/ROOT/ubuntu_w5d0b7 ro
May 31 13:00:17 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_w5d0b7@/vmlinuz-5.4.0-33-generic root=ZFS=rpool/ROOT/ubuntu_w5d0b7 ro
May 28 10:52:58 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_v46mn6@/vmlinuz-5.4.0-33-generic root=ZFS=rpool/ROOT/ubuntu_v46mn6 ro
May 27 18:05:15 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_v46mn6@/vmlinuz-5.4.0-31-generic root=ZFS=rpool/ROOT/ubuntu_v46mn6 ro
May 27 08:00:10 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_v46mn6@/vmlinuz-5.4.0-31-generic root=ZFS=rpool/ROOT/ubuntu_v46mn6 ro
May 23 11:53:15 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_v46mn6@/vmlinuz-5.4.0-31-generic root=ZFS=rpool/ROOT/ubuntu_v46mn6 ro
May 21 18:10:00 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_v46mn6@/vmlinuz-5.4.0-31-generic root=ZFS=rpool/ROOT/ubuntu_v46mn6 ro
May 14 09:30:00 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_v46mn6@/vmlinuz-5.4.0-29-generic root=ZFS=rpool/ROOT/ubuntu_v46mn6 ro
May 08 07:44:57 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_v46mn6@/vmlinuz-5.4.0-29-generic root=ZFS=rpool/ROOT/ubuntu_v46mn6 ro
May 07 19:39:56 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_v46mn6@/vmlinuz-5.4.0-29-generic root=ZFS=rpool/ROOT/ubuntu_v46mn6 ro
May 04 09:57:34 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_v46mn6@/vmlinuz-5.4.0-28-generic root=ZFS=rpool/ROOT/ubuntu_v46mn6 ro
May 03 11:01:42 kernel: Command line: BOOT_IMAGE=/BOOT/ubuntu_v46mn6@/vmlinuz-5.4.0-28-generic root=ZFS=rpool/ROOT/ubuntu_v46mn6 ro
Data from the specified boot (-72) is not available: No such boot ID in journal
Data from the specified boot (-73) is not available: No such boot ID in journal
Data from the specified boot (-74) is not available: No such boot ID in journal
Data from the specified boot (-75) is not available: No such boot ID in journal
Data from the specified boot (-76) is not available: No such boot ID in journal
Data from the specified boot (-77) is not available: No such boot ID in journal
Data from the specified boot (-78) is not available: No such boot ID in journal
Data from the specified boot (-79) is not available: No such boot ID in journal
Data from the specified boot (-80) is not available: No such boot ID in journal
Data from the specified boot (-81) is not available: No such boot ID in journal
Data from the specified boot (-82) is not available: No such boot ID in journal
Data from the specified boot (-83) is not available: No such boot ID in journal
Data from the specified boot (-84) is not available: No such boot ID in journal
Data from the specified boot (-85) is not available: No such boot ID in journal
Data from the specified boot (-86) is not available: No such boot ID in journal
Data from the specified boot (-87) is not available: No such boot ID in journal
Data from the specified boot (-88) is not available: No such boot ID in journal
Data from the specified boot (-89) is not available: No such boot ID in journal
Data from the specified boot (-90) is not available: No such boot ID in journal
Data from the specified boot (-91) is not available: No such boot ID in journal
Data from the specified boot (-92) is not available: No such boot ID in journal
Data from the specified boot (-93) is not available: No such boot ID in journal
Data from the specified boot (-94) is not available: No such boot ID in journal
Data from the specified boot (-95) is not available: No such boot ID in journal
Data from the specified boot (-96) is not available: No such boot ID in journal
Data from the specified boot (-97) is not available: No such boot ID in journal
Data from the specified boot (-98) is not available: No such boot ID in journal
Data from the specified boot (-99) is not available: No such boot ID in journal
Data from the specified boot (-100) is not available: No such boot ID in journal