

Signal is probably best, since it has volume to hide in, and it’s difficult/ impossible to screw up. Partly because it’s centralized. Which is the problem with e.g mateix protocol - each node can configure thi gs a bit differently. Also why you should use the official app imo.
This is a decent walk through: https://www.privacyguides.org/en/basics/email-security/
But simple duckduckgoing can provide much more
https://5blockchains.com/posts/pgp-vs-signal/
https://ubos.tech/news/pgp-encryption-security-crisis-why-cryptography-needs-modern-alternatives/ (feels a bit clanker like - but info is legit)
I like briar for sure. Mostly because it might work if the internet goes blip, and you only have p2p. But… It’s in maintenance mode, exactly because its not easy to use.