Thanks!
That was the issue. For future reference (if someone finds this thread), running scummvm from the command line like this:
fixed the issue for me.

Thank you bgK.

I'm playing Police Quest 4 on ScummVM 2.0.0 on Debian and I get double keystrokes. Now, I wouldn't mind if there was no problem other than my save files being named "tteesstt" but you have to type in the game as well. Any ideas about this? I installed Flight of the Amazon Queen just to tes...