It's the BOOTX64.EFI that the UEFI on that computer doesn't like, just grab the grubx64.efi from whatever the other folder is called and replace BOOTX64.EFI with it.
it should be, yeah. those kernel arguments that are on the steam deck image are soley for the OLED deck, and HTPC users use the same image as the deck. secure boot on desktop images should be fine
let me find out specifically, but it was the one under the releases on github. i did manage to install it once today just fine but because i was just testing in that instance i didn't set things up how i wanted to, and i went back to do it again and i'm getting errors :/
there's only 1 offline ISO that was released months ago. it is super out of date and justfiles have been revamped. if you did, open a terminal and enter: