If it's the compositor that causes the problem, can't it be disabled? I don't know phosh but in Plasma you can disable the compositing from the system settings.
Nope, there's no option for that in phosh settings. Actually, it's the compositor (phoc) that starts gnome-session in /usr/bin/phosh. I've just tried to edit the startup script to launch gnome-session directly, but it would refuse to start.
It's also a pure wayland system, so it's quite unlike what we're used on desktop.
It's also a pure wayland system, so it's quite unlike what we're used on desktop.