I too have this very issue. Zenity 4.2.1 is installed and in my path.
If I run zenity in terminal:
zenity --file-selection \
--title="Open File" \
--file-filter="*.lua *.stl *.obj *.3ds" \
--file-filter="All files | *"
I get a working dialog, which is hijacked by ranger on my system.
In IceSL, if zenity is used for file selection dialogs, why might it behave differently?
I have used IceSL on linux for a long time now. I have always ran it under xwayland and had no issue.
Wish I could debug this and knew more to do so. But then again I may know how to. Maybe with a little wisdom here I can resolve this. IceSL has been my primary slicer and I value it to the point of being stubborn to not print at all.