[yellowapple]

It sounds like in this case the submitter would indeed also be the upstream maintainer.

In any case, it's possible to install Flatpaks without Flathub (by distributing a single .flatpak file to be installed with 'flatpak install --user something.flatpak'), though this is obviously not as convenient. Would be interesting to see an alternative Flatpak repository specifically for Flatpak'd Windows apps.