> Still, I would not switch, because other features, which I use everyday in #Jabber/#XMPP are still missing, e.g. gateways to IRC, Matrix, and SMS.

actually this is not true, there are bridges to #Matrix, #IRC, #XMPP, #WhatsApp and many other platforms via #Matterbridge

but your point still stands valid, if you are a happy xmpp user why to switch? for me it is a no-go for the mentioned problems of xmpp group centralization etc. and difficulty of onboarding