[moamoa]

 
For 4K Netflix you need to have a Netflix-approved box, not just one that has the right Widevine level.  Netflix have a separate approval programme still I believe for their premium streams.

So an N2 would not work with Netflix. You could buy a cheapo Android box, install CE to sd card & boot from android when you want it. But the cheapo boxes are not able to deliver 4K netflix. There is a netflix addon for kodi/CE but when I last tried it, the audio was way off. 
You could buy a nas (expensive) & run sonarr etc on that, & buy a shield (not cheap) or amazon fire stick.

I use the Netflix plugin (and Amazon & Disney+ plugins) on Kodi (LibreELEC) and they work great now. It's my main use for Kodi actually, along with tvHeadend for live TV via satellite. It's this use-case I really want to move to a new setup that can do 4K. My understanding is that (and correct me if I'm wrong) to play DRM content to you need Widevine. Widevine supports both software and hardware decoding, on Linux based devices such as LibreELEC it can't use hardware decoding but can only use software decoding which limits it to 720p on a LibreELEC (on a PI) and possibly 1080p on better hardware that can software decode it. In order to have Netflix 4K you would need hardware decoding within Widevine (which I think is called Widevine L1). There are a number boxes that have Widevine L1. To clear something up here, is the L1 implementation linked to the OS? Can the L1 hardware decoding via Widevine only happen under Android, so Linux running on the same hardware wouldn't work? To continue, additional to this... even if you have Android box with Widevine L1 which is capable of running DRM content in 4K, this still might not work, as Netflix also implement a whitelist of devices that are allowing to use the 4K decoding.

So to get 4K Netflix you need to basically be running one of a very limited number of android based boxes, possibly;
Nvidia Shield
Google Chromecast 4K
Amazon Firestick 4K
Xiaome MI box S 4K

That it's, if you want Netflix 4K. And it must be running the host android OS. Even if you were to root and install LibreELEC on the MI BOX (if that were even possible) the Netflix plugin wouldn't work because the Widevine it would use would be a Linux one and wouldn't have access to the L1 decoding, is that right?

Given all this, it would appear I will need to go from LibreELEC to an android version of Kodi running on one of the above boxes. In this case....

Has anyone tried the Netlix plugin running in 4K within Kodi on any of the above? As this looks my only route.