Related to deprecated ks kernel boot parameters here - https://projects.theforeman.org/issues/32486

ks= parameter supplied by "Kickstart default iPXE" template is rendered, causing RHEL9 to fail to start installation even though inst.ks url should be supplied by the kickstart_kernel_options snippet.

kickstart_default_ipxe.erb = https://github.com/theforeman/foreman/blob/develop/app/views/unattended/provisioning_templates/iPXE/kickstart_default_ipxe.erb
kickstart_kernel_options.erb = https://github.com/theforeman/foreman/blob/develop/app/views/unattended/provisioning_templates/snippet/kickstart_kernel_options.erb

Proposal for resolution - remove "ks=<%= ks %>" from kickstart_default_ipxe.erb line 43. "ks=" or "inst.ks=" should then be supplied by kickstart_kernel_options.erb