@zingaro TBH I have never tried in uefi mode.
As for your note: if these are dell computers, when in uefi mode you need to enable the uefi network stack (on the network page) in the firmware. I assume other OS will have similar options. On the boot options, it will only show valid uefi boot sources so you do need to enable the uefi network stack for that option to show up.
Your MDT boot image should contain the uefi boot kernel. In my case we use VMWare and boot our target computers directly from the mdt iso in uefi mode. They boot without an issue, but again I’m not sending the iso image across the network with pxe.
I can confirm uefi booting via pxe works with these instructions tomorrow since I’m out of the office today for training.