I don't have your problem, It could be that I turn off all services non-related to a single pc.

the KDE login screen has several 'buttons' in addition to the password-box:
   sleep, hibernate, restart, shutdown

these buttons are non-functional on my computer but are working in a QEMU
VM (daedalus+KDE)

KDE login uses sddm (and sddm-helper)

i am guessing this problem has something to do with init (boot-time). so,
testing this idea, i added a delay to /etc/init.d/sddm just before the
"call do_start_cmd"

after adding this delay the login-screen buttons became functional.

testing on this computer shows i need approx 250 millisecond delay to get
these buttons to become functional. 200 milliseconds is not enough.

i would like to know how to determine what sddm is waiting on. how does one
debug timing-related issues like this?