Thank you. I did not know where to look for those available gsettings keys.
For this solution, using my chosen keys which happen to belong to a Chromebook keyboard, the only necessary step is:
gsettings set org.gnome.settings-daemon.plugins.media-keys screen-brightness-down "['<Super>F6']"
gsettings set org.gnome.settings-daemon.plugins.media-keys screen-brightness-up "['<Super>F7']"
I’ll add to the GNOME gitlab issue with a link back here.