you could “dd” your root partition to a partition on that HDD every now and then. and if you don’t have your home on a different partition do that and it’s easy to back this up with a syncing tool if u decided to do that or at least the .config .local and .cache directories because many programs put their configuration files in there.

BE VERY CAREFUL WHEN USING “dd” BECAUSE IT CAN MAKE YOU LOSE DATA FOR A WHOLE PARTITION OR DEVICE

docker keeps some data in ~/.local/share/docker btw