Sending all the voice messages I get to some server? Uhm, no.

Great idea in theory, though.

A bunch of marketing blah blah, I wonder what they’re up to.

I don’t know what would fit your needs, but Signal does not require Play Services. And even if those are present, it does not leak data to Google. Other than “Signal is installed” and “You get a push message”, Signal does not put your messages into the notifications. Instead Signal connects to the Signal servers and then gets the encrypted messages from there and only then decrypts.

Even if you have Play Services installed, you can force it to use a background connection inatead, if you disable Play Services before installing Signal, it wall automatically fall back to it.

If you want a version without Play Services libraries, you could use Molly, a hardened version of Signal, which is available in a version without those libraries.

Molly even allows linking phones as secondary devices, not just desktops.

Matrix is not the right protocol for staying anonymous. There’s way too much unprotected metadata.

You might be able to mitigate that somewhat by using an instance that is accessible via TOR and being careful who you communicate with, depending on threat models and so on.

But if you want to communicate anonymously and not leak meta data… Probably not what you are looking for.

• user names cannot be changed
• never delete your database, have backups, all the state is in there, if you lose your DB, you essentially have to set up a new server: Your server will say you are not in a room while others say you are, so you cannot join. Always keep your DB backed up.

Pretty much the only one.

Though there’s also Neochat fron the KDE F-Droid Repo.