ActivityPub, the protocol that powers the fediverse (including Mastodon – same caveats as the first two times, will be used interchangeably, deal with it) is not private. It is not even semi-…
absolutely nothing posted on it, including direct messages, can be seen as even remotely secure.
If lack of secure DMs are a concern, sign up to Matrix and add your ID into the relevant slot in your profile. You now have a button on your profile for secure DMs
If lack of secure DMs are a concern, sign up to Matrix and add your ID into the relevant slot in your profile. You now have a button on your profile for secure DMs