google 'graphics-drivers ppa for linux'
#Need advice/help with nvidia-340 driver
pallid lance
see their website for further details.
and how to add the repo.
once it's added, open software manager, click its menu, 'update package list', then search for what u need
u could test it out on a live persistent usb. (need to make and enable pesistence using Rufus)
since nvidia drivers need a reboot, that's why persistent-live, not just live
shouldn't matter.
anyway, if u can try that on usb, n it works, jst repeat the same steps u took on the real OS
if not, just reformat the usb
persist size should be id say 3 gigs minimum
the persisten usb would be the guinea pig. u dont actually do anything else affecting the hard drive
that's all ive got
u can also boot-in using nomodeset if needing safemode graphics, to let u fix things
or do a timeshift snapshot
before messing around
if it breaks, u boot live usb, run timeshift restore from that environment
timeshift is easy af.
and u could try a run using a non-encrypted install
til u find a working way