Since the initial post, I tried 5.35 after a rev and found that it worked well. Until today.
I used nvidia-smi this time and was able to see that - although dpkg showed the files installed, the driver wasn’t loaded. I found some instructions from Michael Murphy on [Lemmy.world] that helped to resolve this.
sudo apt purge ~nnvidia sudo apt install nvidia-driver-535 sudo reboot
There’s definitely something funky about 5.35. I haven’t had this problem before and this machine has been stable for a couple years now. It’s probably a good idea to keep this idea in mind when you install the latest drivers.