That's good to know, though any modification to the Mullvad browser should ideally be done as a last resort to avoid fingerprinting.
Rather, is there a YouTube client that integrates with the SponsorBlock API?
I started searching myself and found that too, though I can't even get videos to play on the browser for some reason, even though the instance I tried works through Libretube, which I've been using for a good while now by the way and SponsorBlock is great on it!
I wonder if it's a web client bug
Alternatively, Piped has SponsorBlock built in. It also has DeArrow support, but I find it causes too much of a slowdown so I keep it disabled. Plus, since I only really watch from my subscriptions, clickbait is less of a worry for me.