SDDM is the issue. I suggest using KDM to fix the problem.I used Synaptic and installed KDM and once installed you will get a popup and you can select it as the Default DM.
REBOOT. GAMES ARE FIXED. Next do a purge on SDDM.Everything works beautifully now. The lock screen is the same. Only difference I've seen is the initial login box on a cold start.
Cheers!