alt Hacker NewsDMARC is layered across (/is useless without) two other protocols (SPF, DKIM), both of which also require DNS records.. there's no way to DMARC with one record.. unless you're excluding those SPF and DKIM records in your count. You /could/ DMARC with two records: DMARC+SPF, or DMARK+DKIM but it's ill-advised - use all three. (Ignoring host hierarchy/cname delegation, you can have far more records)
I suppose I'm splitting hairs.
Yes, a proper email authentication stack has DMARC + SPF + DKIM. But each of these is a separate protocol.
This also doesn't take into consideration the other protocols that have arisen BIMI, APRF, MTA-STS / TLS-RPT and are at even lower levels of adoption.