Cool, I'm running a Matrix service like this myself but it's been a bit hit and miss. Keeping all those different bridges running over time is difficult. Especially the signal one is a real PITA, often contacts stop getting my messages from matrix while I still get theirs. And Whatsapp requires whatsapp web so you need to keep the client running on your phone 24/7 or run it in an Android VM which is pretty heavy. And…
> Keeping all those different bridges running over time is difficult. The issue is that most of the services Matrix tries to bridge to are basically hostile entities (except IRC and Slack). I'm honestly shocked how well Matrix bridging works when you take that into consideration -- and unsurprisingly the Slack and IRC bridges are the nicest ones to use. But I will admit that I think Matrix's marketing around bridging…
Most bridges require your own session on the third-party service (sometimes provided by a session cookie in the config file) and then invite you to a private room for each conversation through that service. There is no concept of a login UI for a third-party service, nor is there a concept of "ghost" users for third-party service users (let's say I have a friend that is both on Matrix as well as IRC and Signal - I want him to be considered as a single entity on the UI, and no need to have "rooms" for one-to-one chats with third-party users.