If the market share were compelling enough, couldn’t some other maintainer step up and do this work? OSS doesn’t necessarily mean support for everything under the sun at all costs; Chromium may be open source but that doesn’t mean they have carte blanche from Google to test every possible combination of distro and GPU.
This kind of problem specifically doesn't map to "user finds problem, puts money where mouth is on bug bounty to fix it" because actually figuring out your Blink based browser isn't hardware accelerated is at least a nontrivial task most won't even realize until they go "oh wow whys it so much faster on Windows?" and then not even know where to start looking to find out why.
I'm pretty sure Mozilla just don't care about Linux these days. It's been getting steadily worse, and 64.0 is almost unusable for me due to a bug that has nothing to do with graphics which hangs the whole thing for minutes at a time.
