> the surveillance networks can capture metadata - who talks to who and when
If this is part of your threat model then I would suggest a different tool such as SimpleX since it uses onion routing and can be configured to always use private routing/relays.
Session uses onion routing. SimpleX does not.
I'm not familiar with SimpleX, but keep in mind only some types of onion routing is secure against a global passive adversary. Famously Tor is not.
Nym is apparently good against a global adversary.