Ah, I did not realise that. Thank you!
(I ended up getting a long list of errors when trying to list packages, but I guess it is better to open a new issue for that.)
UPDATE #1:
The error, nix-repl errorr: while calling the 'throw' builtin, only showed up as I pressed enter after pkgs.linuxPackages. So, if I only tabbed, as suggested above, I see all the kernels.
UPDATE #2:
Yes, tab, and not enter, as explained here.