Can you use a proxy server to retrieve a kickstart file?
Solution 1:
It looks like the answer is to use "proxy" instead or "inst.proxy" even though Anaconda will complain when it starts.
menuentry 'Install CentOS Stream 8' {
linuxefi centos-st8/vmlinuz ip=dhcp inst.ks="http://public.example.com/centos-st8-ks.cfg" nomodeset proxy="http://192.168.0.3:3128"
initrdefi centos-st8/initrd.img
}