alt Hacker News> People configure things similar to https://mxtoolbox.com/dmarc/dmarc-setup-cname instructions (which I find in conflict with RFC1034).
I don't think they're advising anyone create both a CNAME and TXT at the same label - but it certainly looks like that from the weird screenshot at step 5 (which doesn't match the text).
I think it's mistakenly a mish-mash of two different guides, one for 'how to use a CNAME to point to a third party DMARC service entirely' and one for 'how to host the DMARC record yourself' (irrespective of where the RUA goes).
I'm not sure, but we're seeing this specifically with _dmarc CNAMEing to '.hosted.dmarc-report.com' together with a TXT record type, also see this discussion users asking for this at deSEC: https://talk.desec.io/t/cannot-create-cname-and-txt-record-f...
My main point was however that it's really not okay that CloudFlare allows setting up other record types (e.g. TXT, but basically any) next to a CNAME.