For trying to get back into your computer, as squid_slime mentioned, check the CTRL+ALT+F1, CTRL+ALT +F234567 etc first, and see if you’ve still got any control over the computer.
If you get a terminal, you may be able to run “top” to show you the top processes currently running, then CTRL+C to close top, look at the ID of Cyberpunk (if it’s still running) i.e. 12345, then run “kill 12345”.
After that you may be able to get back to your desktop - may be CTRL+ALT+F7, but could be any of the F keys really. You may have to go back and kill some other wine/steam processes. If the system is fully frozen, this won’t work.
The other thing to look at is to see what the logs say - I can’t remember if Ubuntu includes a log viewer by default these days, but you can easily get one from your Software Centre (or you can rummage around in var/log if you’re into that kind of thing).
Anyway, in a GUI log viewer, you should be able to see some system logs from when the program was shut down (a drop down menu at the top normally lets you select a time period) - these may help for searching i.e. “why has my Nvidia driver fallen off a bus?” rather than “Cyberpunk crashes my computer when it closes” - because the same error will have probably happened with other programs you’re not familiar with.
Also, when I’ve had these crash-on-close in the past, it was quite often an NVidia thing, and it sorted itself out a few updates later.