I compiled omnispeak for opendingux, it's a reverse engineered commander keen 4/5/6 engine. You can find it here: https://gofile.io/?c=XPi8X4
I included the keen 4 shareware version. I made scripts to start each episode, so just create a link to e.g. keen4.sh. I also added icons. To add data for other episodes, just copy audio.ckX, egagraph.ckX and gamemaps.ckX into the directory, where X is the episode number (4, 5 or 6).
I should add: Tested on an A320, I don't have any newer devices
And: Keen 6 works but it needs v1.4 or 1.5 of the game, you may have to patch it in dosbox.