Reply to comment:

Ross Chandler
I believe 464XLAT support has also been introduced in Windows 10 Creators Update. (https://blogs.technet.microsoft.com/networking/2017/07/13/core-network-stack-features-in-the-creators-update-for-windows-10/) Could you provide more details on what is required to get it working? I tried without success when I connected to an IPv6-only network with DNS64 & NAT64.