Linux Phones

I personally don't use it, but I often see people complaining that they cannot use it on their Linux phone and that might help.

I stumbled across a project which implements the client connection, like the app does, for WhatsApp: https://github.com/WhiskeySockets/Baileys

That would allow building a third-party WhatsApp client.

That should also be relatively simple to integrate into a Matrix bridge such as mautrix-whatsapp. Apparently it uses the same API as the app, but it authenticates as a web client. If someone were to implement the authentication of the app, people could start using WhatsApp without the app and also comfortably bridged to Matrix.

You can still link the bridge to the app currently, but the app needs to be online or the bridge will get disconnected after a few days. And if you don't want to have a phone constantly running, you probably want a VM for the app and then that all gets fiddly.

Also, I recently found a blog post on how to build Matrix bridges, so that should be feasibe if anyone wants to implement that as part of the existing bridge: https://mau.fi/blog/megabridge-twilio/