Secureboot uses the TPM (Trusted Platform Module) to store keys to signed bootloaders (the windows bootloader for example), and then tells the BIOS to not run unsigned bootloaders.
Dual booting is when you install multiple OSs on your system. the most common dual boot configuration is windows and linux. unless you run stock ubuntu, your Linux bootloader is not signed and will not function with secureboot enabled.
as seen in another post here its possible to hack the TPM requirement off, but for how long will this work? temporary fixes, especially security hacks, never last long and are patched quickly.
My recommendation to everyone who doesn't want to be locked out is Virtual machines. Virtualize your windows using QEMU/KVM. libvirt makes it really easy nowadays.
You can set some variables in kvm to get it working again but its still a pain in the ass
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true, thats what I ended up doing too