I love nightlies, specifically with the great Scribus; currently, if a new release happens, I have to download it manually from SourceForge and then install it with Flatpak. It would be much easier to add the development branch to Flatpak and give the user a choice of which branch to install.
Could be added the same way as GIMP nightly, i.e., into GNOME's official nightly Flatpak repository (https://nightly.gnome.org/repo/).