ASUS - ZenTalk

I have an external hard drive which contain linux(ubuntu) system which boots in other laptop. But in asus tuf a15 it doesnt show the option to boot into my hard drive. I have tried "disabling fast boot and secure boot" but there is no option to boot ...

i have registered with my mail through google in rog forum but when i tried to open website it takes me to a loop link : ((rog.asus.com/forum/userupgrade.php)) where even if i put my details the forum doesnt open properly and clicking on option takes...