Depends on the phone and carrier, if i enable tethering (iphone 8) then my connected devices get IPv6 addresses. Some android tethering implementations use CLAT

Depends on the phone and carrier, if i enable tethering (iphone 8) then my connected devices get IPv6 addresses. Some android tethering implementations use CLAT and only give you legacy IP. Some old routers might do the same, or might do so by default until you reconfigure them. Here at least the mobile network uses cgnat for ipv4, but fully routable ipv6 - so the only way i can get inbound connections over the mobile network is to use ipv6.