I'm fairly sure I've seen an NNTP based imageboard that distributed it's content through that protocol and different instances had overlap of boards. That's about the closest match to federated system you're going to find with this model I think. Interesting concept. Not something I'd want to interact with personally though.

Original WhatsApp was XMPP with phone number for your username. Pretty much what https://quicksy.im/ does now.

WhatsApp today is completely different beast.

It's been a year or two, but last time I tried it their app worked fine on x86 Android in qemu. Not the most efficient way to run it, but at least it's isolated from the rest of the system.

I'm not convinced by Session's decision to remove forward secrecy. I don't care if it's malice or incompetence, they shouldn't be in business of encrypted messaging either way.

And their lack of transparency on their share of underlying network and the associated costs for new entrants doesn't make them smell like a cryptoscam any less.

My personal advice is avoid. You'll be far better off with simplex, or xmpp+omemo for something not paired with phone number.

It's been doing the exact opposite and implementing more targeted advertising after several previous monetization attempts (including a cryptocurrency integration) flopped.

Similarly the feature set is increasingly locked behind "premium" paywall.

It's headed in no good direction if you ask me.