To install the browser firefox on my system I used sudo snap install firefox. Afterwards, I installed the extension VideoDownloader, which was working fine. But by using this extension the first time I got the message Companion application required and a button to install this external application. Therefore, I did the requested installation, successfully. I started a second try to download a video. But the same message Companion application required appears.
After some investigation I found the root cause for this. The snap-file for firefox by self is the problem. Inside of file snapcraft.yaml the option of confinement is strict. Therefore firefox can't reached the Companion application, because the installed Companion application is outside of the sandbox. And by security ruleset confinement:strict, firefox has no permission to use the Companion application.
Question: How can I do a change of security ruleset confinement:strict into security ruleset confinement:classic?
2 Answers
You can install Firefox by sudo snap install firefox --classic to do this. I'm not sure if you can convert an already existing install from strict to classic though.
Don't use snap or apt to install Firefox!
Instead, directly download the installer from the official website, and install it by the instruction Install Firefox from Mozilla builds (For advanced users) from : Install Firefox on Linux.
The VideoDownloader then works.
