This PC is Ubuntu Studio but with Xfce installed. Recently the PSU blew, causing power to arc across the room. But having replaced this part I'm able to log in normally - provided I go into Recovery Mode first.
If I leave it to boot normally, I get a flashing cursor. There are other posts about that problem (e.g. Ubuntu 20.04 boots to black screen with flashing cursor) but I believe this is slightly different. At the flashing cursor if I press Ctrl+Alt+F1 I can get to the terminal and log in BUT after an apparently-random time interval of a few seconds I am returned to the flashing cursor unless I press Ctrl+Alt+F1 again. I thought this suggested a hardware problem with the graphics card but when I do get Xfce started (see below) it no longer happens.
I have tried some of the top-rated fixes such as purging the proprietary nvidia drivers, adding nomodeset to grub, and commenting out additional and network disk drives from fstab.
If I try to do 'startx' from terminal under these circumstances it gives an error that:-
xinit: giving up xinit: unable to connect to x server: connection refused xinit: server error
And I was not able to find any advice that worked.
One more thing is that I tried to do a fsck from a 20.04 live-USB and it crashed partway through to a black screen.
WORKROUND
If I go into the grub menu during booting, and select an older kernel, the problem persists.
However, if I go into any kernel's Recovery Mode and then select the option to Continue with Normal Boot, it will boot normally and run whatever programs etc. The problem I mentioned above of it keeps returning to a flashing cursor also ends and I don't keep having to press Ctrl+Alt+F1.
Next I will try and check the boot disk for bad sectors. It is a SSD and I have a vague awareness that sometimes in a catastrophe they can write-protect themselves to prevent data loss. But when I've had problems like that in the past it has usually been that the entire filesystem became write-protected and that isn't the case here.
Otherwise my first question is what is the difference between a normal boot and a normal boot that is initiated via Recovery Mode? Since that might be where something has been damaged.
And my second question is what is the flashing cursor appearing in, if not a virtual console? I thought in X everything was in a virtual console (since even the login is in one, and in Linux the login is almost fundamental) but is this flashing cursor being displayed by something at a conceptually even lower layer, such as the BIOS? Or Grub?
Thanks for reading and hope someone can help
