[vondutch]

Stay on Marshmallow Firmware would be my suggestion if all you need is 1080p Netflix / Kodi with a stable setup. Once you upgrade to buggy Beta versions of Nougat there is no going back to MM.

 read on xiaomi forums someone found a way to go from Nougat to MM preserving DRM

http://daivietpda.com/2017/11/mdz-16-abh...-0-to-6-0/ 

 I've already tried that and it seems a safe procedure, everything is working fine and i've mantained all the DRM i had prior to the downgrade (Widevine L1 and Microsoft Playready), so Netflix works and Google cast also works.