When I updated my system yesterday it upgraded my kernel to the 5.9 realtime kerknel. I had been using the 5.6 rt kernel. It automativaly updated to 5.9. After that I booted to a black screen. This is because this old computer uses the nvidia 340xx drivers which apparently are not supported in kernel 5.9-rt.
The firmware update 20201113.xx also broke the screen.
I ran Timeshift from the command line to undo the kernel and firmware update and am running just fine again on the 5.6 real time kernel. The firmware update also properly rolled back to the 20201023.xx version. Thank goodness for Timeshift.
But now I am no longer seeing the 5.6 real time kernel listed in the settings menu. This is making me real nervous. What happens on the next update?
What do I do at this point? How do I avoid additional firmware updates, for one thing?