I recently setup a little NAS on my RPi, and I also followed similar steps to the article mentioned above.

I also found Tailscale to be useful to access it from any anywhere, and Docker to be useful for automating some of these steps

I wrote a little docker setup that I have been using to automate some of this work: https://github.com/danieldaquino/simple-self-hosted-file-cloud

It does not cover the setup of an external hard drive, but it might help with some aspects