It seem like the ability to install flatpaks during a kickstart in an air-gapped network is possible. The dvd media for rhel10 has a Flatpak directory along side the BaseOS and AppStream directories. The Flatpak directory contains flatpaks for firefox, thunderbird and associated runtimes. If rhel10 can do it surely fedora media can be constructed that does it.
But how do I actually install a flatpak during kickstart?
I have not found anything in kickstart or anaconda documentation and web searches have been fruitless.