Basically any Fossil / Skagen (they're the same thing) Hybrid (meaning e-ink) watch will work with Gadgetbridge. I personally have the Fossil Machine Gen 6 Hybrid which works great. Ignore the 'Alexa' bit, that does nothing via Gadgetbridge (and in fact you can just flat out remove that 'app' in the GB app). Heart Rate and Message/Notification/Call control functions all work fine. Step tracking works, but sleep tracking does not (Fossil doesn't have it done on the watch, it's done in their app, so until/unless GB replicates that functionality it won't work).