How can you mandate that DRM be licensed to clients that can't or won't actually enforce it? That would be mandatory support for copyright violations.
Copyright violations would continue to be illegal. I am not proposing that they be legalized (though copyright law could use several reforms as well). I am proposing that for instance Google ought to be required to license Widevine to anyone who wants to build an implementation for it.
Because Widevine is so widespread and acts as a gatekeeper for content (for example Netflix), if Google doesn't bless your platform with Widevine support you're essentially dead as a consumer media platform.
Google should not have this kind of power because competition is good.
IANAL but seems to me like laws along the lines of "you can reverse engineer DRM without being arrested" and "the patent holder/whatever of the DRM cannot deny you a license to use this without a good reason" seem like the right direction to me. Then the linux distros or anyone else can go off and build/integrate the DRM to the extent that they wish.