The ISP router handled DHCP and DNS for years. It was fine until it wasn't: a firmware update reset the local records and half the house lost access to the printer.
Unbound now runs on the mini PC that already hosts file sync. The router hands out its address via DHCP, with the router itself as the second resolver so nothing breaks when the mini PC is rebooted.
server:
interface: 0.0.0.0
access-control: 192.168.1.0/24 allow
prefetch: yes
local-zone: "home.arpa." staticKeep the fallback. Keep the TTLs short while testing. Write the local records down somewhere that is not the box serving them.