Ubuntu 17.10 is not running Wayland

I just encountered a similar issue to this (gdm3 was unable to launch wayland on my ubuntu 17.10 system) - I resolved it by switching to lightdm.

I was not seeing the duplicate process issues you report, but maybe that will help.

sudo dpkg-reconfigure lightdm

I had a similar issue (GDM3 shows only Xorg session) on dual monitor setup. With only one monitor connected the Wayland session was present. From syslog it seems that GDM fail to start on Wayland when there is no monitor defined as primary and fall back to X.

Solution was to setup a display layout in X session and then copy a monitor configuration file from home directory to the GDM configuration directory:

sudo cp ~/.config/monitors.xml /var/lib/gdm3/.config/
sudo chown gdm:gdm /var/lib/gdm3/.config/monitors.xml

I had a problem with gdm3 and wayland which lightdm did not solve.

On artful (17.10), I first installed the nvidia-384 proprietary driver. When trying to revert to wayland from xorg (removing nvidia driver), gdm3 would not offer a wayland session. I had to edit /etc/gdm3/custom.conf and comment out the wayland line:

#WaylandEnable=false.