To boot an ISO image, in many cases you don't really need a CD/DVD or even a USB stick. A quick and easy way to checkout a new distro is to run it under a VM (via qemu/kvm or any of the other options) and if you like it, you can then just add a grub entry to be able to boot it up on baremetal directly from the hard disk.
Here's a grub entry I added recently to boot the last Gentoo LiveCD ISO image:
menuentry 'Gentoo LiveCD (kernel: gentoo) with GUI' --class gnu-linux --class os { search --no-floppy --fs-uuid --set=root 7d1f62d0-a675-48b7-9fb0-caa9df3eb6c5 loopback loop ($root)/boot/gentoo/gentoo.iso linux (loop)/boot/gentoo nokeymap nodhcp secureconsole root=live:CDLABEL =gentoo-amd64-livegui rd.live.dir=/ rd.live.squashimg=image.squashfs cdroot iso-scan/filename=/boot/gentoo/gentoo.iso initrd (loop)/boot/gentoo.igz }
You could either copy the Gentoo ISO to /boot/gentoo/gentoo.iso on your disk or even setup a symlink from /boot/gentoo/gentoo.iso to the actual file name (in my case livegui-amd64-20250429T205022Z.iso). Here how my /boot/gentoo/ directory looks:
lrwxrwxrwx 1 root root 34 Apr 30 11:11 gentoo.iso -> livegui-amd64-20250429T205022Z.iso -rw-rw-r-- 1 ubuntu ubuntu 3804395520 Apr 30 10:53 livegui-amd64-20250429T205022Z.iso
Note that I've set it up this way with a symlink so that I can replace the ISO image with the latest and update the symlink without having to make any changes to the GRUB entry.
Note: This is just a "note to self" since I had to do some research to get it working and I'm hoping that having it on my own blog makes it trivial to find