External DisplayPort monitor blanks permanently when connected to Thunderbolt port
With gnome-shell 3.31.2 (Rawhide) on Wayland and X. My Dell U3011 monitor connected to a ThinkPad T480 Thunderbolt port, after the screens blank, stops receiving a signal and can only be revived by unplugging and reconnecting.
Expected behaviour is for the monitor to revive with the laptop screen when the mouse is moved. Switching the BIOS Thunderbolt security setting between 1, disabled (Display Port and Mouse), and 2, User Authorization combined with disabling it in the Thunderbolt Settings panel, causes it to behave as expected temporarily--for the rest of the day or until the next reboot. None of the other Thunderbolt settings combinations seem to affect the problem.
When the monitor is unplugged in the process of waking it up, the expected behaviour is for the windows from the external monitor to move to the laptop screen. Instead they stay where they were, invisible and inaccessible. They're still in place when the monitor is reconnected.
On Wayland, Firefox (nightly flatpak or Rawhide rpm), with multiple windows and tabs, crashes about 80% of the times when the monitor is reconnected.