Hi, I tried a lot of times to install KDE (and a lot of other distros like ElementaryOS o Kali) via USB but i wasn't able to do this. When i try with Ubuntu or Windows it works, i can't understand what is happening.
I have the exact same problem.
This is what I'm doing:
1) Download elementaryOS
2) Use the Startup Disk Utility to create a bootable USB
3) Reboot the system
4) Disable secure boot
5) The elementaryOS logo appears on the screen but after few seconds the DELL recovery utility takes over and it shows options to recover my system. The installation of elementaryOS never begins.