2011 Mac mini can’t get past the white screen on startup...then restarts.

Yes I know, it’s a “legacy” product...early 2011 model so can’t upgrade beyond High Sierra.

so on startup, it:

• chimes
• apple logo appears
• progress bar starts moving and gets to c. 2/3 complete..
• brief black screen (this used to lead to desktop)
• white screen with faint vertical lines. This pauses for around 10 seconds....and restarts.

loop.

I’ve read as much t/s as I can find. I have performed all of the following tasks several times in different orders...

• tried to boot in safe mode. This couldn’t be achieved. (Same progression of events as above)
• tried to boot in recovery mode. This couldn’t be achieved. (Same as above)
• reset PRAM/NVRAM. Confirmatory double chime. No change to result..
• reboot in verbose mode, multiple times. Completed, led to same black screen then white screen then restart..
• Tried internet recovery - the world spun.....the progress bar progressed...then same result as before
• boot in single user mode and tried “/sbin/fsck -fy” followed by reboot. No change to outcome
• press start button holding “d”. Got the diagnostics screen and ran hardware test. No issues identified.

is there anything else I can try, short of going to a Genius Bar in the first week of shops opening after COVID?

I know one of the answers is...get a new Mac. That will come... but I need this thing working for now..

thanks!