I'm trying to get DE3815TYKHE to run headless as well (as router to replace the RBP I'm using now). The problems I've been having have to do with getting the boot ordering right. I've found that once the install is completed, when the system reboots the boot drives and their ordering can change and on a reboot sometimes the system comes back up, sometimes it doesn't. Can you tell me what iso you used to install Debian, I'm currently using lubuntu, but would be willing to try what you are using and see if we get the same result.
I used UNetbootin to image a 1 GB USB flash drive with Debian's latest stable netInstall. I then booted the NUC off the USB flash drive and installed Debian to the eMMC storage.
Once installed I removed the USB flash drive, and let the NUC boot from the eMMC. After that, I added an SSD.
I've done some more testing with my DE3815TYKHE, and I have never gotten it to boot without something connected to the HDMI or VGA header.
It's obvious that Intel has an issue with either the hardware they've chosen, or their BIOS (I'm guessing it's an issue with the BIOS). The previous generation of NUCs didn't have this problem, so there's something that's not right.
I'm using my NUC at home, so the headless issue isn't a complete deal breaker, but I certainly wouldn't consider, or recommend, a headless NUC in any production work environment.
Anyway, in all honesty, it's a shame. I feel for the people who purchased one or more NUCs to use as multimedia kiosks or marketing displays, and can't remotely manage or reboot them without something connected (and turned on) to the HDMI or VGA header. Nobody wants to remotely apply updates or reboot a public facing device with the monitor or TV turned on. Right?
Thanks is it safe to downgrade and what are the side effects ? Link to version 24's .BIO file is welcome too
i found the solution
intel nuc boot headless on all bios versions but you have to check the legacy boot option in the bios
tested with version 44 and boot without vga or hdmi attached