Free subdomains are not compatible with Cloudflare.
The rate limit can not be bypassed. All you can do is try to change ACME Provider setting between let’s encrypt and ZeroSSL or:
Use service like sslforfree to create a certificate and download the zip file it provides and extract it.
Follow the instructions:
1. Log on to DirectAdmin Control Panel.
2. Go to the "SSL Certificates" panel (underneath Account Manager).
3. Select the option "Paste a pre-generated certificate and key".
4. Open your Private Key file (private.key) and your Certificate file (certificate.crt) in Notepad and paste them both in the text box.
NOTE : Paste the Private key and then paste the certificate file content
5. When you are done, click Save.
6. Return to the 'SSL Certificates' panel and click 'SSL CA Certificate' (ca-bundle.crt).
7. Paste the intermediate certificate (Based on type of certificate you have get intermediate file) followed by the root certificate in the text box.
OR : Simply Get the CA-Bundle and paste it into the CA-Certificate field.
8. Make sure you select option "Use a CA Cert".
9. Click Save.
10. All certificates are now installed.