I keep encountering ppl trying to use XMPP as a cautionary tale about Threads and it's just... so ahistorical. Yes Google and Facebook did a bait and switch with XMPP, but there was never any thriving network of interconnected XMPP servers they hooked into, stole users away from, abandoned, and left to die. The whole point of XMPP was a promise of being able to connect with Gmail users, and when that was broken, it became pointless.