> The one thing I couldn't make work was the OEM installation, where you put everything down onto the system unattended then put the user through the Ubuntu OOBE process.

Did you try chain booting into iPXE and using SYSLINUX?

I used just nginx try, where I could place a pressed for a known provisioning event, otherwise providing various live and utility images if the MAC address file didn’t exist for one off or emergency repair.

I could even serve up windows instances.

That is also very useful because occasionally you run into PXE firmware that is crippled, it may not apply now, but only having a tiny iPXE image on tftp helps with speed and security.

I would bet almost all vendors just use iPXE anyway, and at least you use to be able to replace the firmware on intel cards with it.