I have an Amazfit Bip 5 with Gadgetbridge and for the most part it works just fine. It even accurately recognizes my bicycle workouts, something my Apple Watch Series 5 could never manage to do. For $80, I am very satisfied.
On the flip side, the Sleep and Do Not Disturb modes let through calendar notifications and sounds no matter what, which is mildly infuriating.
I also deleted the Zepp app after the initial pairing, so maybe that’s part of why my experience is different?