OS's break. Ubuntu is known for having some quirky bugs every release.
Read up on your motherboard's options to be sure, but that sounds like secure boot in hiding. As far as I understand it, Ubuntu is the only distribution that works with it because of Canonical's efforts. You could keep it and dig through why it's not working, limiting you to Ubuntu's community, or disable it and work fine like every other Linux distro.
It is. My ASUS mobo basically has the exact same language for Secure Boot.