Yesterday I was using a little site I threw together for Endless OS¹ and I nerd-sniped myself into making it better (within the constraints):
https://eos-apps.endlessos.org/
¹Endless OS uses Flathub out of the box, but for legacy licensing reasons, there are a handful of these old apps that can’t really be updated that we continue to host on our own Flatpak remote. They never used to be browsable, which made it hard to determine if any should be included in a custom build of Endless OS!