This question involves 3 (!) operating systems, so I hope I'm asking at the right place.
I'm trying to write an Ubuntu ISO image on a flash drive, to be used on a Lenovo PC laptop. I am using a MacOS computer to burn the ISO file with unetbootin, following the official instructions.
The process ends with success, but the Flash Drive is not bootable - when I choose the right option form the boot menu, it tries to read it but quickly fails back to the existing GRUB screen on the Lenovo.
Any idea what am I doing wrong? Can I write an ISO image for a PC using a Mac?