I'm using Blockada for that, which acts as a vpn, but just filters all requests through a big hosts file.
Use with care, as you may break things. I've been using it as-is with no disruptions/problems.
[1]: https://itunes.apple.com/us/app/dnscloak-dnscrypt-doh-client...
[2]: https://itunes.apple.com/us/app/dnscloak-dnscrypt-doh-client...
Do you mean your own dns server which will be accessible to (anyone on) the public internet?
DNS-over-HTTPS spec also mentioned that you can use a standard HTTP authentication if you want to run a DOH server but want to keep it private (although I've never tried this)