If you're frequently distro-hopping, I recommend using a seperate /home partition. I did that before I settled down, I can't begin to describe how convenient it was (especially if you use Flatpak).
To do this one could install the new distro on a new partition, boot to it, delete everything from the old installation except the hone directory, move your user to the base directory (/home/sorrybookbroke -> /sorrybookbroke) before editing your /etc/fstab and mounting the old partition to /home
This way, no external drive is needed like @Luci suggested. Of course, their suggestion is the easiest, but this is the one I personally chose.