There's three Winevine tiers, L1, L2 and L3, which generally correspond to 4K, 1080p and 720p respectively though it depends on the service. L3 is what you get on Linux. L2 is supposed to be more secure than L3 but AFAICT it makes little difference to piracy groups, L1 is the only actual roadblock for them.

Why are Linux users limited to L3?

Because it doesn't meet the requirements for L2. I think L2 implementations are required to block software screen recording, for example, and there isn't really any practical way to enforce that on an open platform. Windows/Android/iOS have special support for compositing protected content so if you try to read the framebuffer back the content just shows up as a black rectangle.

L1/L2 requires a third party who could be liable to sign that the drivers are unmodified to the hardware.

On a general purpose Linux installation who would do that?

(And who in the Linux using community wouldn't take any efforts by someone to try as an afront, bluntly).

Also there aren’t really enough of us watching videos on Linux for it to be a worthwhile market for them to address, I think.

DRM only really works if you're not root on your own machine, and with Linux you're always root on your own machine. Quite frankly I think DRM (the normalization of rootkits) is dangerous.

L3 can do FHD on Linux but it's the services config that prevents that.

Why do they do that?

The lower levels of Widevine protection are weaker, so the content providers like Netflix only allow playback in standard definition or 720p at those levels.

They don't want the highest quality to be available on devices where the DRM can easily be broken.

>They don't want the highest quality to be available on devices where the DRM can easily be broken.

they don't want to admit you can get L3 keymaterial from androids super easily. They just are obnoxious assholes.

So it turns out chrome os ships with a shared library to support L2 (since it's entirely in software). There's a patch to get it working on other Linux distributions.