I built my own NAS, just Ubuntu+ZFS using an old PC I had and it works great. Don't know why people are so crazy about buying prebuilt NASes.
Why wouldn't they be? No fiddling, super compact form factor, (usually) far superior energy efficiency, maybe phone apps, did I mention no fiddling? Also, the form factor!
And often not only the price is high but poor reliability.
It is amazing that no one spoke about security in any of the child comments of https://news.ycombinator.com/item?id=49131785