I installed Fedora (Unix) on my NUC, and then decided that Windows 10 Pro with BitLocker would be a better fit.
1. Reformat the SSD M.2 drive in a Unix shell window from Fedora. Power down.
2. Plug in the Fedora install ISO into the SD port.
3. Boot into a Fedora-Unix system recovery shell.
4. Use Unix commands to remove SSD disk partitions except for the primary disk partition. (Start with higher disk number partitions first working your way down to the final, primary disk partition (0 or 1) that you do NOT delete. Power down.
5. Pull BIOS jumper.
6. Uncrew SSD M.2 drive.
7. Unscrew and flip over motherboard.
8. Pull the CMOS battery plug on the bottom of NUC board.
9. Use a ballpoint pen with a metal tip to clear CMOS plug on motherboard.
10. Plug CMOS battery back in to motherboard.
11. Reinstall motherboard properly so that you can hear a clicking sound when the power button is depressed. Very tricky!
12. Plug in a USB thumb drive (not a SD card!) with the Intel Visual BIOS version 28 on it in a USB port. Power up NUC while BIOS jumper is removed.
13. Click F7 to recover BIOS. Power cycle NUC.
14. BIOS will reinstall. Power down.
15. Replace BIOS jumper. Power up to a black screen. Wait a few minutes for the NUC BIOS to reset. You may or may not see a screen that prompts you to hit enter to install OS. Power down instead of installing OS.
16. Remove BIOS jumper. Power up.
17. Press F2 to enter BIOS setup menu.
18. Setup BIOS settings exactly the way you want them BEFORE installing Windows 10 Pro OS. F10 to save and exit BIOS setup.
19. Plug in Windows 10 Pro ISO.
20. Replace BIOS jumper. Power up to a black screen. Wait for a few minutes for the "Hit enter to install OS prompt."
21. Hit Enter to install Windows 10 Pro. Delete any disk partitions that Windows 10 Pro finds. Continue with Install.