

You could do a vpn hosting by yourself.
Meaning your server is basically a vpn tunnel server and you can connect from the Internet to it. Once you are in the encrypted vpn connection you have access to the local network.
If you have dynamic ip you need dns though. But no one can connect just because they know the ip)/dns
https://wiki.nixos.org/wiki/NixOS_Wiki
Still lacking a bit of information about specific stuff.
https://nixos.wiki/
Unofficial should have the same information, but sometimes there is a discrepancy.
https://search.nixos.org/options
For any option you might need the name of.
https://nixos.org/manual/nixos/stable/options.html
For basically anything else where you just have the implementation documentation