HTTP UEFI SecureBoot works, its just not supported or tested. Just follow our HTTP UEFI chapter but instead "Grub2 UEFI HTTP" PXE loader, choose "Grub2 UEFI HTTP SecureBoot" option. This will make the DHCP server to reply with "shim.efi" filename option which then verifies the signature and passes over to grub2 signed by Red Hat keys. Other workflows like Discovery or Bootdisk are not supported and will not work at the moment. https://docs.theforeman.org/nightly/Provisioning_Guide/index-foreman-el.html#creating-hosts-with-uefi-http-boot-provisioning_provisioning
Upon review of our valid but aging backlog the Satellite Team has concluded that this Bugzilla does not meet the criteria for a resolution in the near term, and are planning to close in a month. This message may be a repeat of a previous update and the bug is again being considered to be closed. If you have any concerns about this, please contact your Red Hat Account team. Thank you.