Better workaround - switch KMS off, Was: debian/testing systems stopped to boot after upgrade between 20.02 and 22.02
I have just found the real source of problem - it is the Kernel Mode Switch
As soon as I have edited /etc/modprobe.d/i915-kms.conf
replacing "options i915 modeset=1" with "options i915 modeset=0"
the problem disappeared on both machines.
So it seems, that this feature may be dangerous (especially it allows
the userspace apps to lock the machine).
BTW it is interesting what has changed between 20.02 and 22.02 which
triggered the problem. There were no changes in kernels in this period
(both machines use my kernels without initrd).
Only a standard "apt-get update; apt-get upgrade" has been done.