Just upgraded from 17.04.
Unity session works. Ubuntu (gnome-shell) on xorg works too.
If I select the default session (Ubuntu on Wayland), after the password, the screen becomes purple, the mouse cursor freezes in the center of the screen and I can't do anything than power off with a single click on the power button.
Don't know if this can help, but after login in Unity session, a dialog error appears, saying
required virtual size does not fit available size: requested=(1,1), minum=(320,200), maximum=(8192,8192)
Obviously it didn't appear on 17.04.
How can I investigate?
Best Answer
I had a gnome-shell extension (freon) that was causing the freeze in my case. Log into gnome with xorg, disable all your gnome-shell extensions and try to log back into gnome (with wayland).
If it works then try to re-enable your gnome-shell extensions one by one. In my case when I enabled the freon extension everything froze...