About that warning on Microsoft Community, I wonder on what it is based? I mean we have two simple, normal DWORDs with a certain value. One (SupportsUUP) tells if UUP is enabled (value 1) or disabled (value 0), the other (EnableUUPScan) tells system if WU can scan the system to see what needs to be upgraded (value 1) or if scan is disabled (value 0).
I simply do not believe that warning. Of course it's a totally other ballgame if (and when) Microsoft simply stops releasing ESD upgrades. Then we have no choice other than accept the fact that UUP is the method to be used to release upgrades. Until that, I cannot see disabling UUP could cause any issues.
Please notice that the above is not a recommendation or suggestion to disable UUP! It's just how I see this, and why I will disable it on each of my Insider machines, real and virtual.
If you want to be sure and take no risks, do not disable UUP in registry.
BTW, EnableUUPScan DWORD will be automatically removed after a reboot when it and SupportsUUP have been disabled (set to 0). A user wanting to enable UUP again must manually re-create that DWORD setting it (and SupportsUUP) to 1.
Hyper-V Enhanced Mode does not support signing in with PIN or picture password. This is because of RDP restrictions; Enhanced Mode is based on RDP and same sign in requirements apply.
Alternative ways to sign in using Enhanced Mode are to set Windows to sign in automatically, or completely remove the password. When removing a user password (local accounts) but still wanting to use Enhanced Mode, the user must be added to Remote Desktop Users group. User without password not in this group cannot sign in in Enhanced Mode.
Hyper-V's normal mode fully supports PIN sign in. All my Windows 10 Hyper-V virtual machines have PIN set to my user accounts and I will always sign in with it when not needing Enhanced Mode.