what is valid.apple.com?

Hello, If I look at my NextDNS log it’s a DNS request by Apple a domain owned by Apple Inc. Since it’s a DNS request and not a website you are not able to access it. If you want to know more about it try a search on Whois with that domain name.

Sorry about that it’s a Certificate validation.

“Apple devices must be able to connect to the following”

please see the link below it should clear things up.

Use Apple products on enterprise networks - Apple Support