Widevine CDM is not available on linux: https://tools.google.com/dlpage/widevine says "Widevine is available for Windows 7 and 8, Mac OS X 10.6 or later (Intel only)". Which means, for example, YouTube TV cannot verify the DRM of the monitor attached to the computer. It still plays, but at a max of only 480p. Because plugin management is no longer supported on Chrome, Widevine is now listed on http://chrome://components. On Linux, you will see that Widevine is not listed.

Since YouTube TV requires Chrome, it does no good to try the widevine plugin in Firefox.

Also, did you notice that Netflix, Amazon Prime, CBS All Access etc don't actually show the resolution of your video playback? Are we getting the same quality of playback as Windows 7/Mac OS X?