I think it’s time to close this one up.
I had some further adventures which are documented in a couple of other threads:
Now I find myself in the following state:
Running 24.04.2 LTS
Everything appears to be functional including the proper screen on Software Updates → Additional Drivers:
Not that I am planning to try to install any drivers beyond 535 anytime soon!!
My experiences with all of this lead me to the conclusion that there is a problem somewhere in the dependency management of the nvidia drivers packages. The final hurdle to be overcome (see the second link above) was needing to run the command
sudo apt reinstall nvidia-graphics-drivers-535
Necessary drivers had been erased by running the command
sudo apt --purge autoremove
After running that my second monitor would not function, and the Software and Updates screen reverted to the “manually installed drivers” message. Reinstalling nvidia-graphics-drivers-535 seems to have returned my system to sanity.
So I am going to call this the answer: I now have a working 24.04 system on my hardware.
There is still an outstanding issue though: If sudo apt --purge autoremove got rid of necessary libraries, thinking them unnecessary, then something is wrong with dependency management of these nvidia libraries. But I will leave that for the Lenovo OEM engineers to figure out.
I’d like to thank all the people who patiently tried to help me on this site:
@ogra
@1fallen
@oldfred
@sgt-mike
@bashing-om
@g-schick
@ubfan1
and any others I may have forgotten
and also Wayne Carter of Lenovo who stayed persistently on the case helping me and demonstrating that they took the problem seriously.
Hopefully this will continue with the remaining issues so that the upgrade to 26.04 LTS will go more smoothly.