What’s the link google gives you to check WebGL?
Well, fingerprinting set to strict is the only reason that WebGL is affected.
You can’t really disable WebGL unless you use the adblocker, which in that case you need a specific rule, in other words, it is impossible for the average user to disable WebGL.
You should test lowering your Shields as a test first and see if it works.
How old or new is your GPU? because you can try to update your GPU drivers. What OS are you using?
But WebGL depends on your videocard, you should go to brave://gpu and see if something is not supported as it should, so it should look something like this:
If the GPU is too old and doesn’t appear to support hardware acceleration, you can enable the Hardware Acceleration by this flag brave://flags/#ignore-gpu-blocklist
if you go to here, do you see the WebGL aquarium working? https://webglsamples.org/aquarium/aquarium.html
There is not much to do, it is all about your computer, GPU. Maybe an extension you have is not allowing webgl to work properly or maybe Shields and especially fingerprinting protection set to strict which doesn’t let webgl to work as it should, but normally and by default, webgl should ‘just work’.