They don't have WebGL on linux, they have a "webgl if available" thing which is mostly not available.

I've heard that when available (never was on any linux machine I've had in my hands and tested since firefox introduced webgl, after a while I started disabling it to protect from the webgl vulnerabilities), it performs poorly compared to other browsers.

Nowadays it works as widely as on other operating systems, just with the abovementioned performance caveat.