phonehelp I'm using a Huawei Watch Fit 3 together with Gadgetbridge and everything works quite well.
You have to connect it, though, to the Huawei app if you want to update the watch.
And one drawback for me is the "AGPS" that is not working with Gadgetbridge. So if you want to use GPS with the watch alone, the first GPS fix takes around 10 minutes in my case. Sometimes it's quicker, but for a quick satellite fix you usually have to update the AGPS-data via the app regularly. Gadgetbridge does not do that. What Gadgetbridge can do, is, to send Smartphone GPS tracking to the watch during a workout. So together with the phone at least this works.
As far as I know this AGPS-data-thing works with Garmin, though. But I don't have personal experience in this regard.
So tldr: if you need GPS on the watch without a connected smartphone, the Huawei might be a bit slow.