Bootable USB for an ancient Macbook Pro 13" 9.2 (mid 2012)

I’ve been driving crazy for the past 3 days trying to make a bootable USB drive to install High Sierra on a Macbook Pro 13" 9.2 (mid 2012) with 0 success rate. Tried Transmac, dmg2img on Ubuntu, I even tried to create the EFI partitions myself and copying the image files over, but the Macbook Pro will not recognize any. I really have no clue what are the requirements for a boot device for this computer, so I’m lost in the woods.

Anyone has any idea how to make a bootable USB drive for this ancient Macbook Pro?

A bit of googling suggest you need to hold down thee alt-button while booting for the boot-menu to show up.

Other than that, have you tried booting the stick in another computer? You won’t be able to install, but maybe you’ll get a more specific EFI message.