I figured out a quick, easy way to install Puppy for multi-booting without leaving Ubuntu (or some other Linux OS), probably in under 10 minutes if I didn't yap so much in this video.
Maybe this is known. I just hadn't seen it done this way when I was looking for how to do it.
EDIT - I made a new video starting with partitioning, and ending with a grub menu ready to multi-boot with Puppy Linux here --> https://odysee.com/@trawg:3/pupinstall:d
https://odysee.com/@trawg:3/2401060449:1
menu entry template - https://disk.yandex.com/d/JFa6Z8_wGkpJYw