I would avoid CloudFlare as non-paying customer. Their free tier limit is 1k domains. Might sound like a lot, but if you run multiple subdomains (e.g. dev, stg, prod) in kubernetes using dynamic domain registration (e.g. external-dns), you'll hit that limit quickly.
To compare a popular service, Route53 (no affiliation) limit is 10k and they won't charge extra if you want to increase the limit, all you need to do is open a support ticket explaining the use case.
Hmm according to OP "A few years ago I bought two domain names on Epik.com", I doubt he wants to have more than 1k domains. Of course your use case doesn't fit the free-tier of CloudFlare but I wouldn't rule it out for all the other people that just want something that works from a legit company that cares about their users and the internet.
To compare a popular service, Route53 (no affiliation) limit is 10k and they won't charge extra if you want to increase the limit, all you need to do is open a support ticket explaining the use case.