I’m running Lubuntu 18.04 and I have the Firefox addon Video DownloadHelper installed. For some operations, Video DownloadHelper needs me to install their Companion App, which is a separate program that I have to install on my system, there’s a DEB file available. According to the website, the full code of the companion application is released in open-source to ensure full transparency, which can be found here. I’m really reluctant to install third-party applications to my operating system. Is it safe? For those who will say, use YouTube-DL, I have that installed also. The reason why I have Video DownloadHelper installed is because not all sites are supported by YouTube-DL, so I use Video DownloadHelper for those unsupported sites.