On the newer machine, the P50, I reinstalled 17.10 ubuntu yesterday, with pre-release packages enabled. It is using gdm3. It works, even with nvidia modeset=1 and external monitors. It is not obvious to me which updated packages have fixed this, since I also tried pre-release on the broken install. The conclusion is that I had something broken in my configuration. I uninstalled X and the desktop environment a few times, which didn't work. In pure Nvidia mode, not Optimus, I am offered a Wayland session, which seems to work (I only did a few minutes of testing).
My broken install was an upgrade from 17.04. When 17.10 goes beta, I will install 17.04, fully update it, and test a migration to 17.10. If this doesn't work, I will seek help to track down which configuration settings could cause this. It is certainly encouraging that it works from a reinstall. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1706474 Title: gdm3 nvidia modeset=1 is broken, external screens don't work To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1706474/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs