Don’t do Element, Matrix is a nightmare (and a significant commitment) to self host. Other servers (recently, continuwuity) are a bit better on that front, but then you run into compatibility issues and edge cases as a forever second-tier citizen.
My advice is to just go with XMPP and ejabberd, and you will find clients for all kinds of usages and people (a free-er WhatsApp takes you to Conversations/Quicksy/Cheogram/Monocles/Monal, a better banquet/IRC-style rooms takes you to gajim/fluux, social networking and group calling takes you to Movim, etc).
Personally my needs are covered by Monocles on Android, Gajim on the PC, and Movim on occasions. Using multiple clients around the same protocol and account is a strength, not a weakness.

Seems wise. They seem competent in the front-end/client space and complete amateurs in the (difficult) protocol space. There is no example of successful tech (that I know of) that successfully added federation/P2P after the fact. It’s not an afterthought, it probably won’t ever happen.