We are running Windows Server 2019 with Windows 8.1 guest.
Custom scaling on host ist set to 130% which is perfect setting for our eyes to work on computer screen all day.
According to this blog post https://blogs.msdn.microsoft.com/virtualpcguy/2016/06/23/hyper-v-ui-updates-for-high-dpi/ in enhanced session the guest gets all dpi information from the host.
This needs to be fixed so we can revert to custom scaling again.
However the modern ui does not scale correctly. Start screen, charms bar and settings pages are way too big. Apps cannot be started, error message is "This app can’t open. The screen resolution is too low for this app to run"
Only predefined DPI settings on host make the guest work, so it is either 125% which is too small or 150% which is too big.