Sunbird and the Function and Strengths of Bridges

So this is interesting: this messenger will provide iMessage to Android users, along with other messengers such as Facebook Messenger and WhatsApp.

Right away, the concept of Matrix bridges come to mind.

Though, the promise Sunbird makes sounds too good to be true. Or maybe I would like to know better about bridges and how they work.

  • What exactly are bridges? It does not appear that you can (for instance) use Facebook Messenger via a bridge without a Facebook Messenger account. Similarly, it appears I wouldn’t be able to iMessage someone on Sunbird without my own Apple iCloud account.
  • Suppose I use Matrix to chat on Discord. What security and privacy benefits does this provide?
  • Are bridges plug and play? Like, if I use Element and try to join a Discord server, the bridge will let me join and interact.
  • If bridges are a wonderful tool for interoperability, why are they seemingly not very commonplace?
  • If possible: what is different between Sunbird and Matrix functionality-wise?