I had a similar issue, but (dumb) lucked into a solution.
Dell Optiplex 3040, BIOS set for UEFI: Onboard NIC (IPv4) first, Windows Boot Manager second.
Installed Win10 Enterprise from USB. After the install and first time on the desktop, before installing anything else, a reboot would come out of the UEFI network boot with Preparing for Automatic Repair. (I gave it plenty of time — about 14 hours! — never got past that screen.) I installed again and got the same results.
I made one change in the BIOS: added a check to ‘Enable Attempt Legacy Boot’ and then installed again. This time, at the first reboot, the screen went dark and … nothing. Manually powered off and back on and was able to log into Windows. But the next reboot, again the screen went dark and stayed that way. So I removed the check from ‘Enable Attempt Legacy Boot’ and now Win10 is working fine, normal reboots, exiting from the UEFI network boot into Windows.
Hope that might be helpful to someone.