I don't know of any ISP that will give you a public ipv4 address for free.

More interesting is windows 11 auto configuring ipv6. Does you pc have a public ipv6 address starting with 2:: or fe80:: link local address?

Quick ipv6 crash course. Instead of DHCPv4 (there is DHCPv6 but it's optional) being required for address configuations, ipv6 uses somting called Stateless address Autoconfiguration (SLAAC). Normaly your router sends out Router advertizments packets and this tells devices about the default gateway, public prefix, dns etc... and pc will generate a public ip of (64 bit public prefix):(64 bit random number).

It seems like Windows 10 and eariler will not do ipv6 unless your router advertises it.

TL;DR learning ipv6 is easier than disabling it at this point