Like I said, the Video Download Helper addon is available on Firefox on Solus.
This is the Companion app who is difficult to install because only .targz and .deb packages are provided on the official website of the add-on.
I'd wish how to know to install it on Solus so. Solus who is not a Debian based OS.
And YouTube-dl don't worth it for what I want to download. Video download helper companion app is more specific.