It does work with Firefox plugins, there just isn’t a button to open the extension “store” in the extensions settings page like stock Firefox has. You can add them by manually going to the url though, it’s just recommended that you don’t since that increases your risk of adding a malicious plugin or being fingerprinted, etc. I still added a few plugins that I really dislike not having though, like a password manager and darkreader, just because I valued the convenience slightly more than the added security.