Installing mainline 6.1 resolves the issues again. Now running:
Linux 6.1.12-060112-generic #202302141939 SMP PREEMPT_DYNAMIC Tue Feb 14 19:45:10 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
UPDATE: Mainline 6.1 breaks other things. Screen is flickering from time to time, more annoying than the sleep/ resume problems. Back on 5.15 for now.
Installing mainline 6.1 resolves the issues again. Now running:
Linux 6.1.12- 060112- generic #202302141939 SMP PREEMPT_DYNAMIC Tue Feb 14 19:45:10 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
UPDATE:
Mainline 6.1 breaks other things. Screen is flickering from time to time, more annoying than the sleep/ resume problems. Back on 5.15 for now.