But now we have dns over https too?
EDIT: Ah, perhaps you meant that with DNS over HTTPS, MTAs will need an HTTP client anyhow. IMO the path of least resistance will be adding HTTPS, DNSSEC, or w'ever to machine-local resolver services. But point taken (whether earnest or sarcastic =)
Then update /etc/resolv.conf with your DoH option or old legacy..
... Not a fan of DoH but it doesn't matter if I like it.