Bug#809086: gdm hang when switching virtual terminal or logging out

[Martin Tang]

I believe I have the same issue, right down to Wayland sessions (which I 
haven't used before since it's not the default) being unaffected.

One "workaround", if you can call it that, is to ssh in and run "sudo 
systemctl restart gdm". This still leaves some of the previous processes 
running, but there are some fresh ones and a fresh gdm to log in with again.