Hello all, I have MATE-17.10 installed on my DELL laptop/tablet. Ive created a live USB of kali-linux-mate. I can boot to the uefiboot list with F12 but when I choose the drive I get a secureboot policy error. If I disable secureboot from bios settings, I cant boot anything including the main ubuntu MATE OS… Just a black screen. I initially created the USB per kali instructions with dd and then recreated it with Startup Disk Creator, both with same issue. I created a live ubuntu-mate USB in windows to install ubuntu and that USB wont boot now either… Anyone got any ideas? everything I search says to disablr secureboot, but that leaves the whole system literally a black hole.
You should be able to boot the an Ubuntu live USB with Secure Boot enabled. I do it frequently. Kali is closer to Debian IIRC, which does not work with Secure Boot enabled. Why the Ubuntu one won’t boot now I don’t know 
OK, Ill try again… Is there a way to get kali to boot from the USB. Idealy what I wanted to do was put kali on another hdd for my Daughter
OK I got the ubuntu live usb to boot. I dont know why it wouldnt the first time. Ill have to consult the kali forum for the kali usb as it seems the issue is the ability for kali to boot with secureboot enabled. Thank you @elcste.
[SOLVED]
OK guys, I figured it out. At least for this little DELL tablet/laptop deal. When you hit F12 to get to the EFI bios, at the very bottom of the list, there is an option for secureboot options. There you can choose to disable secureboot and still use EFI boot. I was going into the standard bios to disable secureboot,making ubuntu unbootable as well because disabling in regular bios turns off The UEFI boot option in the machine. I literally had to go google EFI bios bcause I knew I had it but hadent really needed to mess with it.