This is actually not a plasma 5 issue, SDDM (Simple Desktop Display Manager) is a separate project from Plasma, it's just the recommended display manager. You can technically use any display manager you want, you just wouldn't be able to have it match the lock screen, etc.
Besides changing the permissions did you also change the ownership to ensure that the file was owned by root and not your user?
The only time the avatar file (face.icon) should be owned by the user it belongs to, is if it's in that users home directory. Anywhere else on the system it should be owned by root.
Besides changing the permissions did you also change the ownership to ensure that the file was owned by root and not your user?
The only time the avatar file (face.icon) should be owned by the user it belongs to, is if it's in that users home directory. Anywhere else on the system it should be owned by root.