I’m using Librewolf (a Firefox fork) and have the same issue.
Just check Firefox messaging folder exists in your home
ls -l ~/.mozilla/native-messaging-hosts
In my case, I needed to create a symlink to make it work with my browser
ln -s ~/.mozilla/native-messaging-hosts ~/.librewolf/native-messaging-hosts
Maybe you could apply a similar workaround. Hope this helps
I switched to KISS launcher after I knew the company had bought the project. Never came back.