well i think unstable but questioning that now as I don’t get the same output as your eval commands?
vagrant@carverlinux ~/nixos (master) [1]> nix-channel --list
nixos https://nixos.org/channels/nixos-unstable
vagrant@carverlinux ~/nixos (master)> nix eval nixpkgs/nixos-22.05#terraform_1.name
error: getting status of '/home/vagrant/nixos/nixpkgs/nixos-22.05#terraform_1.name': No such file or directory
vagrant@carverlinux ~/nixos (master) [1]> nix eval nixpkgs/nixos-unstable#terraform_1.name
error: getting status of '/home/vagrant/nixos/nixpkgs/nixos-unstable#terraform_1.name': No such file or directory
sudo nix-channel --update should do (unless you use flakes, which I doubt after the output of nix eval above).
Though be careful then… If you used the 2.3 experimental CLI a lot, then the 2.10ish one will be completely different from what you are used to and also push you towards flakes quickly.
Enabling flakes will not disable channels, any you can use a channel based system configuration for the time being.