I’ve been on librewolf for years, and as long as I’m running the FlatPak version, all Firefox extensions work. Having said that, you do have a few options to sync. One is using your Firefox account (I don’t suggest you do because of Mozilla’s BS over the past year or so, but you would be sharing way less stuff this way). In my case, the only thing I want synced in browsers is the bookmarks, so I use floccus extension in every browser, floccus app in android, and host them all in a self-hosted linkwarden instance. I hope that helps.