Hello!
The machine is ASUS B1500C laptop, with Intel i5-1135G7, 16Gb RAM, Samsung 512 NVME SSD.
The system is freshly updated from 15.3 into 15.5., installed on USB SanDisk UltraFit 32Gb, UEFI, GRUB2, secure boot enabled. Prior to update system booted properly, but couldn’t detect NVME and audio device. The new kernel is 5.14.21-150500.55.19, DE is KDE with no tunes.
Boot hangs soon after taking the password to encrypted /home volume, and not responsible to any keys and combinations except power button hold. Still hangs with recovery mode or runlevel 3.
System boots into semi-working state using old kernel (5.3.18-150300.59.106) from GRUB boot menu: DE is broken (startKDE: could not start kdeinit5. Check your installation), TTY login succeseful.
Looking forward for you assistance, thanks in advance.
It seems you did not read the general rules for an successful upgrade:
Do not skip a release when upgrading! Example: do not upgrade from 15.1 to 15.4. Instead, from 15.1 upgrade to 15.2, then to 15.3, and only then from 15.3 upgrade to 15.4.
I have reinstalled root partition clearly, but it didn’t solve the problem, and now I can’t even boot into CLI with old kernel, because there aren’t any.
So I think the problem is not connected with ignoring the upgrade order. Maybe I can get some other suggestions?
There should be an advanced options menu in Grub containing rescue and/or failsafe boot selection(s). Did you try any of that? Those should result in boot messages that should spell out what happened last with clues to problems. Hitting ESC as soon as the Grub menu exits from the main selection also should give you messages. If you can’t read them due to tiny size you can append an option after striking the E key in the Grub menu, to the end of the linu line to specify a lower resolution screen mode that will result in larger framebuffer text, e.g.: video=1440x900 or video=1024x768 on a 1920x1080 or 1200 screen, or video=1920x1080 or video=2560x1440 on a 3840x2160 or 2400 screen.