Hello,

I'm sorry but we don't officially support A type records yet, for now we only offer official support for CNAMEs, this means you would need to use Nameservers that support root level CNAMEs.

Sadly my customer bought several domains where provider doesnt support root level CNAMEs.
Is it worth a pain to try to make it work via Cloudflare? And is it free as I only need to change DNS provider I hope?

You only need to change the nameservers, you don't need to transfer the domain, Cloudflare has a very easy guide here -

Okay, Ill try that, thanks

!s