Thank you for your report and rating.
We are constantly working on the improvement of our video downloader for further versions.

Unfortunately some features could not be provided by extension since changes in Firefox 57.
Companion application is contain instruments used for downloading streaming video segments.

Thank you for your report and rating!

Version for macOS and Linux is under development atm.
You still can install old AVD in Firefox 56 and below from here: https://archive.ant.com/firefox/AVD-FF-2.4.7.50-Release.xpi
We are sorry for any inconvenience caused and hope for your understanding.