@blankzapper Well as they say the pcap doesn’t lie. Your computer IS saying that its a bios based x86 computer. Your dhcp server is sending the proper file and I see it booting into ipxe getting an IP address again and then pulling up the default.ipxe script that leads to the iPXE Menu. So your computer is working perfectly. Not how you want, but working as designed. Now I assume when it exits from the iPXE menu that is when things go bad. (because the disk structure is efi and we are pxe booting in bios mode. So the bios default exit mode SANBOOT should be called to mount the disk and boot.
So now in your bios (firmware) do you need to enable the uefi network stack? On the dual boot systems they don’t typically come with the uefi network stack enabled in the firmware. I would focus on the firmware settings because outside of your computer everything is working as intended.