[tetha]

cloud-init does help us, once we have a working linux, but we can also bake the static route into a base image.

The problem is that preseed is a very minimal linux environment and either relies on DHCP to work, or to use the usual network config DHCP sets (address, netmask, gateway). Arbitrary routes are not a possibility there. And ways to run abitrary commands to just <ip r> something come after the network initialization, which fails in that setup. The same holds for the kernel network bootstrapping parameters, I haven't found a way to add an arbitrary route there yet.

And for some reason, kickstart is able to handle this with it's centos/RHEL base.