You can’t change the nameservers of a domain registered with Cloudflare Registrar as is indicated at the time of purchase or transfer of the domain.
You shouldn’t need to as in most cases you can point at your hosting using A/AAAA/CNAME records, check with your host for details. Or, if you give the host, someone may be able to point you the right way.
If you do need to change nameservers you will need to transfer the domain out to another registrar.
All I need Cloudflare for is the domain name registration. I have my own hosting. I did not understand that I could not change my nameservers when I applied for registration. I have had different DNS servers over the last couple decades and this is the first time I have been told I can’t change my nameservers.
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