Does ~/.mozilla/native-messaging-hosts actually contain the gnome connector .json file?

Usually packets don’t install files into the users home. You have to see where the packet put the json and then link it into the native-messaging-hosts directory.

(And finally link that to .librewolf as you already did)

it won’t let me install any add ons or plugins.

what?

just install the plugins like normal. Why does it not work, what is the error?