To use pre-built binaries,
wget https://substitutes.nonguix.org/signing-key.pub
mv signing-key.pub nonguix-signing-key.pub
sudo guix archive --authorize < nonguix-signing-key.pub
sudo -E guix system reconfigure config.scm --substitute-urls='https://ci.guix.gnu.org https://bordeaux.guix.gnu.org https://substitutes.nonguix.org'