

Cloudflare has been excellent for me since I switched away from (puke) GoDaddy years ago. They don’t try to upsell you bullshit like most of the other places, either. I have three domains with them.
I do not use any other Cloudflare services. There are no additional costs or services required (beyond the domain fees) to use them as your registrar.



Looks like they allow it, but only if you’re an enterprise customer.
https://developers.cloudflare.com/dns/zone-setups/zone-transfers/cloudflare-as-secondary/