I have no idea what this is about, but this comment sounds like it was posted from the 90s. Do we also need to compile an extension to support playing *.wav files in it?
Sorry, couldn't resist... :)
I believe MiddleClickAutoscroll was broken in last "stable" GNU/Linux version. I can check once I'm on my laptop.
https://forum.vivaldi.net/topic/102072/no-autoscroll-on-midd...
The proposed solution didn't work by the way. I uninstalled right there.