Laptop running 22.04 with a second external display.
For months, I've been running these joined (extended). Then I encountered the Mesa upgrades issue, which meant Chromium didn't display properly. I recovered from this and all was working as before - but only for a day. When I started the laptop the next day, the second display was backlit, but black, except for my pointer, which moved around as normal. Literally nothing else displayed on the external display, but if I mirror the displays, everything works as normal. I believe I've accepted some other updates, but am not sure what they are.
Thanks for any ideas.
Installed NVIDIA packages as of 1 Aug 2023: