Hi Jeffrey, I started to look at this between #1 and #2. My Dell is AMD Radeon, but the Toshiba Satellite in the laundry is Intel-Nvidia.
The Toshiba is where I bottle my beer, a place of significant importance, and so I was going to take a look while I was bottling, but I may not get there until tomorrow.
To keep you going a little, one of the articles I found was this
https://www.linuxbabe.com/desktop-linux/switch-intel-nvidia-graphics-card-ubuntu
... and that was found with a Google of "linux how change default graphics card at startup"
Ubuntu has a few more tweaks up its sleeve than Mint in this regard, apparently.
I suppose a "palm to head" might be that perhaps you did not take a Timeshift snapshot before you started fiddling with Graphics, and I would suggest that that is a must. Hard to fix something if you can't see it (although it can be done).
You are on a learning curve so big your sneakers must be getting overworn on one side from leaning into the curve.
Cheers and it's Friday here so of course to all
Avagudweegend
Wiz