Hi I'l like to give a comparison of two machines here
Desktop running IPv6 tunnel and serving out my routed prefix via SLAAC
Laptop picking up on the tunnel prefix and getting a valid v6 address.
I Have a website running in IIS on the desktop and I also check the address using an external check whatismyipaddress.com
Edge reports being connected to my site using it's IPv6 address
but whatismyipaddress.com shows my public v4 address
Edge reports being connected to my site on my public v4 address
but whatismyipaddress.com shows my Laptops public v6 address
Using a different browser e.g. Chrome shows my v6 address in all instances on both machines.
Can I assume this is some weird Happy eyeballs issue?