/
. Now the installer creates a gpt partition table on the drive with a bios_grub partition for the bootloader, an EFI partition (for booting UEFI) and an ext4 partition for /
. If your hardware is old, it may not recognise a bios_grub partition = no boot.
This guide explains how to install mint the "old fashioned" way:
https://foxclone.org/guides.html
Lots of screenshots, newbie friendly!