Thank you both for your input so far. For plotlinus I followed the instructions Brent has shown above. I think it was once included in the GNOME version of Solus, but I didn't find it in the repo. I also created /etc/environment, but deleting that did not help.
It complained that some configuration file connected to com.worldwidemann.plotinus could not be found, so I ran
gsettings set com.worldwidemann.plotinus:/com/worldwidemann/plotinus/default/ enabled true
For espanso I installed the Appimage and ran
espanso service register
# Start espanso
espanso start
I also changed settings in the WindowsShuffler Gui, but I suppose that this should not break anything.
Any way to reinstall just the display manager and to reset the corresponding configuration?