The venerable Firefox Plugin "Video Download Helper" has been a mainstay of internet video downloading for years. However since I upgraded to Ubuntu 22.04 it can not ever find the "Companion App" it needs to work.
(I did not find a satisfactory answer in this related question.)
Suspecting it was the sand-boxing used in the Firefox snap package, I removed that and used the .deb package as per the instructions on OMG Ubuntu install Firefox as a .deb.
I've tried both the .tar.gz and .deb versions of the companion app. When the app installs, it reports that it's installed correctly:
# sudo ./net.downloadhelper.coapp-1.6.3/bin/net.downloadhelper.coapp-linux-64 install --system VdhCoApp: VdhCoApp is ready to be used
But then in the plugin does not work (tried restarting firefox, reinstalling plugin, etc.). If you go into the plugin configuration, there's a Recheck button in the "Verifying Companion App..." section, but clicking it does not seem to do anything.
How can I make this plugin work with Firefox 100.0.2 on Ubuntu 22.04?
EDIT: Same question for 21.10, with possibly useful answers.