Keeps asking me to download a "Companion App" in order to download videos, and absolutely NOTHING about this is written in the extension description.

It leads you to their own website so you can download and install their app, which gives them access to you files and could be very dangerous. The purpose of extensions is exactly to contain their effects within the browser only, which is safer.

Feels extremely suspicious, and the fact that this is "recommended" sincerely strengthens my recent thoughts of abandoning Firefox altogether.