This is because librewolf reports itself as firefox for privacy, and vivaldi does the same thing with chrome. Their is no vivaldi string in their user agent.
That makes sense. Vivaldi uses a chrome user agent most of the time, unless you use a Microsoft service, in which case it uses a Microsoft Edge user agent.
It got my OS right, but browser wrong. Tested both Librewolf and Vivaldi, which it sees as Firefox and Chrome.
This is because librewolf reports itself as firefox for privacy, and vivaldi does the same thing with chrome. Their is no vivaldi string in their user agent.
That makes sense. Vivaldi uses a chrome user agent most of the time, unless you use a Microsoft service, in which case it uses a Microsoft Edge user agent.