How to backup a Debian system (no images, no installed binaries).

I was wondering what is the best way to backup a Debian system manually without copying installed binaries, just a list to re-download them again. My plan it the following:

Back up a list of packages and repo keys.
Code:dpkg --get-selections > ~/Package.list
sudo apt-key exportall > ~/Repo.keysBack up /etc
Code:rsync -aAXv /etc /mnt/backupBack up /home
Code:rsync -aAXv /home /mnt/backupI'm not sure what should I exclude from /etc and what other directories I might want to backup.

For example, the fstab and the grub configuration files in /etc probably must no be copied? Because the new system needs its own after a clean install.

Also, I use snap and it stores some configuration files in /var/lib/snapd
In general, should I backup the whole / and exclude let's say the /bin folder?
But what about /usr/bin , /usr/local/bind etc...
I'm losing my mind thinking all this stuff.

I usually don't install stuff manually or using make install. Any precompiled or
compiled projects from the source are being stored in my home directory with all
their depedencies.

So what should I backup?

Thanks.