Here's what you can use an old turnkey prebuilt NAS for

Prebuilt network-attached storage (NAS) hardware is excellent for newcomers to the NAS world and those who simply prefer to have a turnkey system ready to go. Simply throw some drives inside and you're good to go. But there may be a time when you look to expand beyond the limitations of a prebuilt enclosure running proprietary software, which is where DIY servers come into play. There's no need to throw the old NAS away as you can repurpose it for other projects, including backup destinations, home surveillance, game servers, and more.