Seems it could be possible to add support to Appimages for native looking appearence. I think this link can be useful: https://github.com/AppImage/AppImages/issues/88
Mmh native looking AppImages sure would be nice. The issue’s still open, though, so it looks like there are still issues to be solved for it to become possible. Of course we could also try to cook up something ourselves but since those “native” styles rely on non-Qt system libraries that would probably be a little tricky if we don’t want to inflate the size of our AppImages by a lot. That said, I haven’t read through the entire discussion of that issue yet, so we might be able to find some hints there.