https://caniuse.com/webgl
https://www.khronos.org/webgl/wiki/BlacklistsAndWhitelists
If your GPU driver is blacklisted, you may try to force-enable webgl in the browser by toggling
webgl.force-enabled;false and restarting the browser (depending on actual GPU, this may work or not, worst case scenario: the browser crashes upon launch - you'd have to restore that pref back to false by editing the prefs.js file in your profile...).
It is needed by the mapbox API they're employing for displaying "Server Location"; as for actual deprecation, the Wikipedia entry for it is unclear about this; .. If you mean WebGL 1.0, well yes, this has been superseded by WebGL 2.0, but the latter is still being maintained, I think:
https://www.khronos.org/news/tags/tag/webgl
But then again, I'm not a gamer myself, so perhaps within the context of video games, the WebGL technology has been surpassed by newer APIs... That doesn't mean it's dead for simpler graphics tasks within a browser,,,