NSA221 resources?

I dug out my old NSA221. It's basically been sitting in a box for years. I'd like to download the manuals, check for updated firmware, etc. However, I see no support links on the Zyxel site for this model. Where can I obtain them?

edit: I did find this, but still doesn't contain the user guide or quick start guide:
ftp://ftp.zyxel.com/NSA221/

#NAS_Mar_2019