Please have a look at the warnings in the comments:
@petsoi@discuss.tchncs.de you might want to add that warning to the post.
They also tried to submit the app to Flathub, but had way too broad permissions with no explanation why. “Users expect filesystem access” etc. In the end it was rejected and they publish a .flatpak file themselves.
https://github.com/flathub/flathub/pull/5233
The other points are far worse though.