Installing Ubuntu 24.04 on Foreman (not Katello)

Problem:
I can’t get Ubuntu Server 24.04.3 LTS to network boot while following Foreman :: Provisioning Ubuntu Autoinstall and other documentation

Expected outcome:
Ubuntu installer runs

Foreman and Proxy versions:
3.13.0

Foreman and Proxy plugin versions:

foreman-tasks 10.0.1
foreman_ansible 15.0.1
foreman_bootdisk 22.0.2
foreman_dhcp_browser 0.1.2
foreman_discovery 25.0.0
foreman_fog_proxmox 0.17.1
foreman_git_templates 2.0.0
foreman_remote_execution 14.0.2
foreman_templates 10.0.1

Distribution and version:
Rocky Linux 9.5

Other relevant data:
I’m trying to provision Ubuntu Server 24.04 and running in to some problems.

First, Foreman :: Provisioning Ubuntu Autoinstall and other pages tell me I need to put a bunch of files under /var/www/html/pub, but since I’m not running Katello that directory isn’t used. I put the snippet from Katello in /etc/httpd/conf.d/05-foreman{-ssl}.d/06-pub.conf and created /etc/httpd/conf.modules.d/alias.load, which works, but it gets clobbered the next time I run foreman-installer. I understand I need to put something in custom-hiera.yaml, but it seems to be intentionally undocumented. Any suggestions?

[While I was typing this up I decided I want to troubleshoot my other problem further myself.]