1- You need a Google account. 2 - The UX is not as good as Termius. 3 - The UI looks like garbage, but does it's job. 4 - You need to selfhost a server.
Well, I have a Xiaomi Mi Band 7 wristband.
Gadgetbridge supports everything you can do through the official app.
Except it doesn't upload data to the manufacturer's cloud. Everything works locally, because that's what it's all about. The UI looks ugly, but what to expect from a project created by volunteers, not a multi-billion dollar corporation? :) Overall, I'm satisfied!