XMPP via Slidge
slidge.im
Very similar to Matrix’s approach but backed by, I think, one developer and some contributors, it’s an ecosystem of bridges for the XMPP protocol.
I do love the XMPP protocol. While being more than two decades old, it’s stable and lightweight even for the current age and time. The protocol’s simplicity makes it ideal for connecting obsolete devices.
Current Limitations
Still, sadly, when I tried to use it in combination with the Slidge WhatsApp bridge, it always reached a point where I would send back to my receivers the messages they had sent me.
Maybe it got better. If you are interested in contributing in any form to this project, I don’t think the maintainer will bite you!
Why XMPP Matters
Despite the current issues with Slidge, XMPP remains one of the most promising protocols for obsolete device communication due to its age, stability, and minimal resource requirements.