From looking at the github, I think you don’t need to/want to host this publicly. It doesn’t automatically get and store your information. It’s more a tool for visualizing and cross referencing your takeout/exported data from a variety of tech platforms. It’s just developed as a web app for ease of UI/cross platform/ locally hostable.
You definitely use a firewall, but there’s no need for NAT in almost all cases with ipv6. But even with a firewall, p2p becomes easier even if you still have to do firewall hole punching