As far as I know, the only official chat channels is #nixos (and #nixos-* friends) on Freenode (https://nixos.wiki/wiki/Get_In_Touch). There is an unofficial Discord, but I'd advice you to join the IRC channels instead, fast help and the people contributing to Nix actually hangs around as well.

I've actually had terrible success getting help through the official channels: it's why I asked.