A very simple (Dutch) guest portal setup for Ubiquity UniFi.
In the Guest Control section of the Unifi Controller setting, select the Legacy JSP template engine and place these files in /Applications/UniFi.app/Contents/Resources/data/sites/default/portal. Check the option Override templates with custom changes, just to be sure.
The Guest portal is available at http://<hostname>:8880/guest/s/default/.