Gatgetbridge (your link) has a breakdown of devices they support https://gadgetbridge.org/gadgets/ . You can click through the vendors to find devices which are both “highly supported” and “no vendor-pair”. Meaning most/all the features work without any reliance on the vendor app.

As for the similarity you are asking about with pixel->GrapheneOS, there are very few watches that can run an alternative open source firmware or operating systems apart from the ones that are already open source, like bangle.js, pinetime, etc. Wearables are even more specialized than phones, they require specialized code designed specifically for them and would likely require pretty extreme effort to reverse-engineer.

I use a pebble 2 HR with gadgetbridge but the watch it self runs the old pebble firmware which gadgetbridge talks to. This is fine for me, but if you are looking for a more modern watch you may have to make some compromises.

AOSP gallery that comes with GrapheneOS. The app info says it’s called com.android.gallery3d. There’s some info here in the docs about the relationship between camera, edit functions, and the gallery app.

No, I don’t have markup installed (it is there in apps but not installed from the mirror).

I think in my case the screenshot functionality is built into AOSP and the editor you get when tapping the resulting preview overlay in the lower left corner of the screen is part of the “gallery” app since using the “edit” feature from gallery launches the same editor. Maybe GrapheneOS just sets that as the default editor, I’m not sure.

What android OS do you use? On stock Android 14 (GrapheneOS, but it’s not a GOS feature) this functionality is built into the stock screenshot tool.

pwr+voldown -> tap screenshot that appears in the overlay after you take it -> tap the crop tool . I suppose step three could be removed but what if you want to do something that isn’t cropping? There are lots of other features so at some point you have to tell the tool what you want to do.

broad support for generic smart watches

Gadgetbridge is pretty well on it’s way to this. They roll out support for new devices monthly it seems like. Of course there are always feature X and Y that fitbit or garmin does that it doesn’t, but it’s quite an impressive project. I use it with a pebble 2 HR.