[Zeus]

The only way for him to use SSL Certificates not issues by CloudFlare while still having CloudFlare's protections would be to upgrade to CloudFlare Business which costs $200/month. I am unsure how funded this forum is. It may or may not have the funds to do so. That being said it's a matter of whether it is worth it or not. In addition LetsEncrypt must be installed on your server and I believe it checks your DNS to determine whether to issue the SSL Certificate or not. Due to the second reason I think it'd be even more difficult to get a certificate issued. There isn't a good reason to switch to LetsEncrypt. CloudFlare provides signed SSL Certificates to install on your web server if you are worried about the security of the connection between CloudFlare and Sinister.ly. They provide several tools to their users to ensure everything has "top-notch" security. Is there a reason that Sinister.ly needs to change their SSL CA? If you are having issues (with an older browser) it's likely we can assist you in "trusting" the "COMODO ECC Domain Validation Secure Server CA 2" and remove the SSL Errors.