If you operate Raspberry Pi as an IPv6 tunnel endpoint or IPv6 gateway , then “every computer on the LAN” can be reached worldwide with its own global IPv6 address. Everyone can access these computers from the outside if an IPv6 address is known from the LAN. It is not the way you know it from IPv4, it can hide behind a router via NAT.
The consequence of this is that you have to make sure that an appropriately configured IPv6 firewall is active on Raspberry Pi.
- Set up an IPv6 firewall on Raspberry Pi to prevents unwanted external access and permits desirable access.
- Check if the firewall works.