I had never used Waterfox, but I installed it just now, to see why it doesn’t work. Latest Waterfox is apparently based on Firefox 102, which doesn’t support Manifest v3 extensions (and Lemmy Go is one of those). I tried to see if supporting v3 and v2 was feasible, but it’s just too many changes even for a relatively small extension like this one. The changes themselves aren’t too big a deal, but it would mean maintaining and testing two very different versions of the extension (which I already have to do for Firefox vs Chrome, but right now they are almost identical). I’d rather keep the project as simple as possible for now.
I expect Waterfox G6 (which is supposed to release in September) to support Manifest v3 extensions, so maybe we just need to wait a bit.
Looks like it’s not working for you. The extension is supposed to work without setting a preferred server. The instance list is supposed to be pre populated. Something must have happened that prevented it from getting the list. Also, when you click save, it’s supposed to show a popup from the browser asking for extra permissions, and then in the Lemmy Go window there’s supposed to be a text at the bottom saying “validating instance…” and then “success!”, or some error. Is the rest of the extension working for you without setting the instance? It’s weird because the instance list comes from the same place as the community list used for the suggestions, so I’m wondering why one would fail but not the other.
I’m working on an update that will show better logs for errors like these.