You don't have to do that (use Legacy). I directly manage ~150 machines, and indirectly ~1500 more, and ALL of them are UEFI, and many of them have been reimaged using external boot media. Real simple.
For most stock installations of Windows10, UEFI is set and so is "Secure Boot" enabled. Unless an admin bios password had already been applied, you can disable SecureBoot, reimage, and then re-enable once you're finished. This keeps those machines secure from those who might want to bypass security by booting their own media. Btw, once done, then is a good time to apply that bios admin pwd.
We use Dell machines for Windows here on campus, and it is EASY to apply a script that does all the above, reboots, allows for reimaging, and then tidies up again at the end...without having to manually change settings in bios at all!
Still very interested in seeing example(s) of such scripts. (Probably would not matter if geared towards a particular imaging program, as long as this could be adapted for another.)
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