good stuff to know.
I miss the days when a disk partition could simply be marked bootable. And I don't think UEFI has made the process any more secure. If anything, it has enlarged the attack surface.

Infuriatingly, on my Acer notebook I must hit F12 right after powering on, and select the GRUB entry, otherwise it just boots Win10. I admit that I have not done much research on it, but have failed to find a way to edit the UEFI boot order.