linux – Attempt to install the Xmonad package hidden

Probably just a big case of PICNIC, but when I tried to install Xmonad, I get error messages

Module "XMonad" could not be loaded
It is a member of the hidden package "xmonad-0.15".
You can run ': set -package xmonad' to view it.
(Note: this unloads all modules in the current area.)
Searched locations:

How can I fix these errors? Did I forget steps? etc.

I have Haskell and Xmonad installed via:

Install ghcup
ghcup set
ghcup install-cabal
Kabal new update
cabal reinstall cabal-install
Reinstall Kabal Xmonad
reinstall cabal xmonad-contrib --lib
# Other potentially relevant information
ghc-pkg list # does not display xmonad or -contrib
ghc --version # 8.6.3
cabal --version #
xmonad --version # 0.15