For the DMARC record “v=DMARC1; p=reject”, the Cloudflare DNS UI shows the following notice: “The record content has to contain a valid policy tag: p=none;, p=reject;, p=quarantine;.”
This message is incorrect. A trailing separator is not required per the RFC: rfc7489
It’s also fairly uncommon to have. Google, Outlook, and even Cloudflare don’t have a trailing separator in their DMARC records.