>With Matrix you can use F-Droid build of the client. And you don't really need to trust the server too much, right? Maybe it's not enough for Snowden, but it's better.

And why should I trust F-Droid's build of Matrix over Signal's build of Signal?

Please understand, I agree with your point. Mine was orthogonal: If you are under threat from motivated and/or state-level actors, using someone else's servers (or clients, for that matter) is a bad idea.

And that includes Matrix. I run my own Matrix server and the users of that server can interact (especially via voice/video) without any fear of being intercepted -- even by me.

What's more, I can't decrypt the conversations folks have in Matrix "rooms" that don't include me without a long process of brute-forcing.

No one is coming to my house to confiscate my server. That scenario is much more likely with a public/commercial service hosted at a data center/cloud provider.

So yes, Matrix is likely more secure than Signal if, and only if you build and install your servers and clients from source with a compiler/linker you built yourself using a trusted tool chain on hardware whose components you've personally confirmed to be free of compromise[0].

[0] https://users.ece.cmu.edu/~ganger/712.fall02/papers/p761-tho...

I like Matrix, but I admit its E2 EE rooms seem to leak more metadata (users in th room, reactionss, maybe replies, display names, avatars) than Signal.

They leak metadata to the operators of the server. So does Signal, albeit anchored to SGX nodes they pretend they cannot access. Signal also has phone numbers making even worse.

With matrix at least you can pick a server operator you trust to provide your metadata to, or host a server yourself.