What I tried: I created the file
/etc/sddm/sddm.conf (also tried
/etc/sddm.conf) with the following content:
[General] HaltCommand=true RebootCommand=true
Unfortunately, that did not help - the reboot button continued to work. Preferably, the buttons should also go away.
Edit: I'd like to clarify that I'm not expecting
true to be interpreted as a boolean value, I'm expecting it to be interpreted as command. And
true is a valid command as there is the executable
/bin/true on most Linux systems that does nothing except returning exit status success. Just to be sure that this is not a path issue, I also tried setting it to
/bin/true which also did not help.