@Renato: I might have a fix for external display in 18.10. If it works correctly, I'll backport it to 18.04.
@Luiz: Gdm 3 creates one main X (or XWayland) session, and then starts an additional X for the user session. It's the default behaviour.
I suspect PRIME synchronisation is only meant to happen with the internal display by default. This is beyond the scope of this SRU though.
@Renato: I might have a fix for external display in 18.10. If it works correctly, I'll backport it to 18.04.
@Luiz: Gdm 3 creates one main X (or XWayland) session, and then starts an additional X for the user session. It's the default behaviour.
I suspect PRIME synchronisation is only meant to happen with the internal display by default. This is beyond the scope of this SRU though.