Cross-posting here from the GitHub issue I opened a couple of days:
Previously, I was able to use both my laptop and an external screen using nvidia sync mode (hardware.nvidia.prime.sync.enable = lib.mkForce true;).
After upgrading to 22.11, when using sync-mode, my notebook screen turns off completely (black screen, no backlighting) during boot/X-Server startup, while the external monitor works fine. Consequently, xrandr does not list my notebook screen (usually eDP-1) in this setting.
I tried booting with the external screen plugged in and plugged off, but in neither case the notebook screen remains on.
Note: I have a muxless GPU, which complicates the whole process from the start (see this PR #165188)
Additional context
I have a muxless Nvidia GPU (Thinkpad X1 Extreme Gen. 4), which complicates the whole process from the start (see this PR #165188)