Installed, but the button to translation is nowhere to be found. Restarted my Firefox, restarted my laptop. Unfortunately, this ads-on appears to be non existing.
UPDATE: It's 80.0.1 (64 bit). But actually while searching for that information I've found out that I am using anonymous browsing, which was blocking the add-on.
All is well now, I am changing the stars. Also I do appreciate your concern. Thank you.