Downgrade Apple TV to 7.5
I've downloaded Apple TV software 7.5 from https://ipsw.me/download/AppleTV3,2/12H885 and the Finder info says it was downloaded from http://updates-http.cdn-apple.com/2020/ios/061-27784-20200313-6EA1D1F6-A6E5-40CB-8C61-B9680241903C/, which apparently is an Apple server.