What I’m looking for ultimately is a universal chat type app like Beeper that can handle Signal and SMS, however, reading this about it gives me pause. It would be nice if I could get all my peeps on matrix, but since it was so hard to get them on to Signal, I think the best I can hope for is something than can handle matrix, signal, and sms. Which brings me back to the title, how exactly do Matrix bridges work and are they secure?
EDIT: SMS is insecure by its very nature, yes?
This is a great point that you bring up. I subscribe to an IRC channel that has bridges to both Telegram and Matrix. My feelings at this point, is that the weakest link is going to be of the most concern. But how all this technology interoperate with each other and how they actually handle privacy/security together is a question I cannot answer.