Old thread but with the right title 
Until recently I had problems switching my auto-login system to Wayland. Where before changing setting files was needed, it is now possible to switch to Wayland using KDE:
- Open KDE Settings (System → System Settings)
- Startup and Shutdown
- Behavior (button left under)
- Then change the “with session” to “Plasma *Wayland)”
Also SDDM has been updated, with lLogout there is no wait anymore on the SDDM X11 session being terminated.