Debian.

The Zimaboard is way overpriced, for a way underpowered CPU. Unless you specifically have a need to use its PCIe slot for something, I see no reason for it.

As others have noted, an ultra small form factor PC, the likes of Dell/HP/Lenovo sell is always a better value option.

Tautulli?

I use Technitium DNS for all my DHCP/DNS/Ad Blocking.

https://technitium.com/dns/