I use Beeper on Android to have one app through which I send messages on WhatsApp, Signal, Telegram, LinkedIn, Facebook, Instagram etc. I never cared for iMessage support.
It works great for me. No support for complex things: calls, message requests, and probably a few more. But most days I don't need to open any other app, and when someone asks me which network they can contact I honestly just don't care anymore. They all look exactly the same on my phone.
How much would you think this degrades Signal security? I don't know exactly how the Signal bridge works, but Signal's putting so much effort into security and the people use it through an app like this one not vetted by Signal, it can't be too good I assume...