This seems like at least somewhat FUD.>>10310>Matrix IDs mapped to Email addresses/phone numbers added to a user’s settings.
I have and am using my matrix acc without having provided an email or phone number. It is only some
free-of-cost host providers that require that at signup. >Every file, image, video, audio that is uploaded to the Homeserver.
A reason many adopted matrix in the first place is because it extended the functional integration of double-hatched encryption to rooms and other stuff, but as is often observed within the rooms on matrix: people often turn encryption off
because they believe it is "too slow" (which to me is a stupid statement but I digress).
If the metadata collection is as bad as they make it out to be even for clients that aren't Element, that use privacy-respecting homeservers, and that have end-to-end encryption enabled for all comms, then I guess the best fallback would be XMPP with OMEMO (Gajim client, for example).