> So now I have a large script which debootstraps a Debian based NAS into being.

Is part of this publicly available? After seeing, - https://words.filippo.io/frood/ - https://0pointer.net/blog/fitting-everything-together.html

I've been looking at setting something up with mkosi/systemd for my home server/NAS - it's interesting seeing how different setups are solving the problem for inspiration.