This is probably due to DRM which is poorly supported by Linux (lazy devs will probably just exile Linux completely). But I do remember some linux-only decoder issues in the past. Decoder and codec support is just poorly signaled overall, even if an API says it supports it, it may not support a specific profile or even support it well.

Some of our video test grid machines are Ubuntu, so from our end Twitch video should work pretty well on Linux :-)