You don’t need the GUI. There is instructions on Rays site.
But if you have a configured image done via the GUI then just copy the configuration file manually
(On GUI config image)
cat /etc/wpa_supplicant/wpa_supplicant.conf
On ospi image edit (nano or vi) that file and replace contents.
The other thing to try is to do a patch of the system (apt-get update). That might download a working GUI