Project information: Beeper is a service (built on Matrix?) and collection of apps that promises to bridge all the chat networks/apps/protocols (I know I know we’ve been here before). They have a desktop app, currently built for Linux as an appimage. They do not have any dedicated Linux developers, but at least one of their desktop devs has a Steam Deck 
Name: Beeper
Homepage: https://www.beeper.com/
License: Proprietary, though they’re very open-source-friendly
Upstream has been contacted: Yes, currently in talks
Since they currently have an appimage, I wonder if a first step could be to get a manifest on Flathub that grabs and uses that, get their app verified, and then work towards a better long-term solution?