The VNC incompatibility is precisely why I had suspected the issue might be connected to this. The machine that crashes does NOT run a VNC server. It runs a VNC viewer to log into a different computer that runs the VNC server. To test my theory that this might cause problems, I never started the VNC viewer after rebooting the Ubuntu 26.04 machine. The system still crashed. It seemed to take longer which is why I was hoping I had located the problem but alas, it still crashed.
I have installed the TigerVNC viewer and will see if running it instead of the RealVNC viewer makes any difference.
Earlier, I tried installing a different desktop environment as well as X11 but I have spent years in the standard Ubuntu desktop environment and switching was too much of a shock to my old fart brain so I abandoned that idea.
I have several headless machines (Raspberries) that run RealVNC servers. They are all controlled via this computer(Ubuntu 26.04) and my second computer running Ubuntu 25.10. The Raspberries had to stay with a fairly old version of the Raspberry OS in order to run a RealVNC server. I was not prepared to switch the Raspberries OS's and run a newer VNC server (again, old fart trying to run newfangled software and a royal screw-up is pretty much guaranteed).
I have installed the TigerVNC viewer and will see if running it instead of the RealVNC viewer makes any difference.
Earlier, I tried installing a different desktop environment as well as X11 but I have spent years in the standard Ubuntu desktop environment and switching was too much of a shock to my old fart brain so I abandoned that idea.
I have several headless machines (Raspberries) that run RealVNC servers. They are all controlled via this computer(Ubuntu 26.04) and my second computer running Ubuntu 25.10. The Raspberries had to stay with a fairly old version of the Raspberry OS in order to run a RealVNC server. I was not prepared to switch the Raspberries OS's and run a newer VNC server (again, old fart trying to run newfangled software and a royal screw-up is pretty much guaranteed).
