Except that the Element web-client also phones home to matrix/element mothership.

The message editing thing is just a client setting and having a single source of truth for a room is a huge advantage of XMPP that Matrix is now reinventing as they realized their hyped decentralized rooms are just a gimmick feature that causes more problem than it solves.

That article is mostly FUD, but there are very good reasons to be sceptical of Matrix, as it is mostly driven by a VC funded for-profit company.

If you are looking for a truly community driven and owned alternative, check out XMPP: https://joinjabber.org

So Chromium?

Just use Firefox, its the better browser anyways.