Andrew, many thanks for the explanations.

Some of my projects only need the social network part and would rather rely on already popular messaging solutions, preferably those that are also known for respecting privacy, such as Signal.

Would it be easy to create a connection between Signal and UNA to override UNAs messaging system ? I mean, people would link/declare their Signal account (probably by just adding their associated phone number) to their UNA profile and every time a user wants to chat with his friend from the UNA-based web site/app, they would be sent to a conversation on Signal with the selected recipient(s).