I am planning on upgrading my machine to the new Ubuntu 20.04 LTS (possibly Mate) by a clean install. I have a one terabyte external disk that I plan on copying my home directory (152.8 GB) to. This is in case something goes completely haywire, I'd at least have a copy of my old home folder. I have used my current setup (Ubuntu 18.04 LTS) for about four years now and may have tinkered with files in root directory here and there to provide certain files in path and all. To the best of my knowledge, I have all of those files in my home as well.
But just to be safe, are there any other directories in root I should make a copy of? Why?
In addition to this, is there any checklist I should go through before doing a clean install?
Here is how my root looks right now,
user@machine:/$ ls --all
. cdrom home lib32 mnt run sys vmlinuz
.. core initrd.img lib64 opt sbin tmp vmlinuz.old
bin dev initrd.img.old lost+found proc snap usr
boot etc lib media root srv var