I've been wanting to switch to Linux on my Pro X SQ2 for a while due to the WSL2 support on it being terrible (might be fixed now [1]) but always thought that most stuff such as LTE, webcam and surface connector wouldn't work [2].
The peripheral support is slowing getting there.
The major issues are the ones you've mentioned (including the inability to use external displays), but I'm seeing more and more upstream commits for the sc8180x by Maximilian - so I'm confident that these issues will be solved relatively soon.
Wi-Fi and BT works btw, which IMHO makes it already usable as a daily driver. Audio works via BT
