Hey @tlauwk!
In order to re-enable the Provisioning template, you can make use of the userdata interface of Foreman. Have a look at these changes. Then, you have to define a userdata template for the OS and select it for the host. This gives you the option to make use of provisioning templates as usually. This line must be changed accordingly:
APPEND ip=dhcp url=http://<%= @preseed_server %><%= preseed_path %> autoinstall ds=nocloud-net;s=http://<%= userdata_server %>/userdata/ root=/dev/ram0 ramdisk_size=1500000 fsck.mode=skip
It references the userdata interface instead of pointing to a static file. The variable userdata_server points to the corresponding smart proxy and must be initialized as followed:
userdata_server = foreman_url('').sub(/.*:\/\//, '').split('/').first
userdata_server = @preseed_server if userdata_server.split(':').first == foreman_server_fqdn
Be aware that this won’t be the final state of the template - the PR is still in review and might change, but it should fix your problem for now.