WebGL doesn't load
Haven't been able to find a clear answer on this, so I'll just ask. Is anyone else having trouble getting WebGL content to render? I know it's not a hardware issue; I can run get.webgl.org through Firefox and it works fine. Is it a Chromium bug that's disabling it, or is it Vivaldi itself?
I suggest you disable/remove your extensions and check again.
vivaldi://gpu/to see if webgl enabled for Vivaldi.
http://get.webgl.org/ & https://www.khronos.org/webgl/wiki/Demo_Repository also work on me.
Works for me.
Please check by opening vivaldi://gpu if WebGL is off.