Normally if you run nix search <package> it will complain about something experimental.

Assuming you read the message and understand what you are getting yourself into, follow the instructions to enable search. Alternatively, you can search on

Put the following in ~/.config/nix/nix.conf

experimental-features = nix-command flakes

Now search will work but it will rebuild cache every time you search. To avoid building cache, run nix registry pin nixpkgs.

Search packages with nix search nixpkgs <package>.