@epilys I have no clue about using the OS resolver but:
https://crates.io/crates/simple-dns only has one dependency, bitflags, and allows you to create DNS packets. Sending the query using a stdblib socket and parsing the answer using simple-dns should them be a matter of not too many lines of code.

Another option, if you already have a crate to send https requests in your dependencies, is using DNS-over-HTTPS from cloudflare or Google:
https://developers.cloudflare.com/1.1.1.1/encryption/dns-over-https/make-api-requests/dns-json/

https://developers.google.com/speed/public-dns/docs/doh/json

@laund

Overriding the user's DNS preferences would be a problem... unless it's opt-in

The real problem is finding out the system resolver. POSIX libc gives you nothing :/ So there's no portability for BSDs, macOS, GNU/Linuxes, GNU/Linuxes with systemd etc