@jonw @thenomad Do you mean a DNS resolver (the type you use to resolve names to IPs) or an authoritative server (the sort that keeps the authoritative records for some specific domains)?
I built my own personal Linux wifi router, which runs it's own resolver, out of an old mini PC. It's fantastic (faster & a lot more secure than the junk available in stores), & pretty easy to set up too! I run Unbound DNS server.
Feel free to ask if you have any questions!