This issue was related to a bug with the installer where "%base-packages" was not added to the system configuration file.¹ After working around the installer issue as described in the manual,² I can read manuals normally.
1. https://debbugs.gnu.org/cgi/bugreport.cgi?bug=35541 2. https://www.gnu.org/software/guix/manual/en/html_node/Guided-Graphical-Installation.html#Guided-Graphical-Installation --- https://sirgazil.bitbucket.io/
