because the last two or three years I've became very forgetful just had to follow my tracks trying to reconstruct the way I get to work an old Puppy Linux version (3.0.1) in a PC from 2001 without booting from USB capabilities on the BIOS, and it seems it was about using Rufus to make a pendrive bootable from the Puppy ISO and adding PLOP Boot Manager to the GRUB2 install belinging to a Debian install on the HDD of that computer, but I totally forgot the details
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@ordenauta been there, have the usb stick. Don't know how I made it.
@b4cks4w if it helps, check the root level of the usb stick and look for any txt file that may had any clue about the software you used to make it bootable (except if you used dd or something like that info could be not available)