IPv6 tunnel without IPv4?

Question

openvpn

Hello!
There is a local network. You need access to the central server, PC and phones. But WAN IPv4 is not. The provider does not block ports, but it cannot issue IPv4 and IPv6 either. How do I get an IPv6 tunnel in this case (OpenVPN, IPSec or whatever)?!
Requirements:
1. Free of charge
2. Ability to access via IPv6 from outside.
How to implement this?! Tell me please!!!

Answer 1

https://tunnelbroker.net/ for help.