Yesterday I struggled for a few hours to get Hyper-V installed w/o losing the host internet. I even updated from W10 x64 v1909 to v2004 but still no joy. After reading other peoples advise to fix it, I used my own notes & discovered that IPv4 was unchecked in my Ethernet properties, after checking that I added the Google public Preferred & Alternate DNS server addresses, clicked OK & about 20 seconds my host (OS) internet was working again.