Currently, in CloudFlare Pages, upon addition of a custom domain, the service will detect whether the root domain is managed by other CloudFlare accounts, and if so, a DNS migration will be required.
However, I am running open source projects using the js-org project’s subdomain, js-org is sponsored by your company. Obviously the js-org community runs the DNS management on their CloudFlare account; but if I want to setup a js-org custom domain on CloudFlare Pages, it will ask me to transfer js-org to CloudFlare (i.e. my CloudFlare account), which is impossible. However, the js.org project is fully happy for its subdomain to host various static page hosting services.
I would like to suggest CloudFlare to remove the check on root domain owner, or add an option to simply use CNAME to setup the custom domain (or maybe with an additional TXT record to prove ownership. This way, a lot of subdomain users on the js-org project could be benefited.
I hope you can consider above suggestion seriously. Thank you.