https://matrix.org/blog/wp-content/uploads/2017/02/2017-02-0...
> Matrix does not protect metadata currently; server admins can see who you talk to & when (but not what). If you need this today, look at Ricochet or Vuvuzela etc.
> Protecting metadata is incompatible with bridging.
> However, in future peer-to-peer home servers could run clientside, tunnelling traffic over Tor and using anonymous store-and-forward servers (a la Pond).
> But for now this is sci-fi.
https://github.com/matrix-org/synapse/issues/2188
https://github.com/matrix-org/synapse/issues/4565
Signal, in contrast, put a lot of effort into metadata reduction--critical as they are a single giant hosted relay service--and in the process (I am very sure) even fixed the issue I used to complain about wherein their server was technically keeping around a temporary-ish in-memory metadata log for rate limiting.
https://signal.org/blog/sealed-sender/
If you are going to switch to something, switch to Signal (...though I sadly can't in good faith ever really recommend anyone do that, due to how Signal has crippled the ability to do chat backups; more info on this in the other thread going on today re Signal/WhatsApp).