Regardless of whether or not you provide your own SSL certificates, cloudflare still uses their own between their servers and client browsers. So any SSL encrypted traffic is unencrypted at their end before being re-encrypted with your certificate. How can such an entity be trusted?
That’s not end to end encryption, it’s two seprate ssl connections both terminated at cloudflare. One from client to cloudflare, one from cloudflare to your server. Cloudflare is still a MITM inspecting your traffic in that scenario.
They do however let you disable their proxy(WAF) service, acting as pure DNS so clients connect directly to your IP instead of theirs. But they can at any point toggle that back on and intercept your traffic, nothing really stopping them except morals and T&Cs, but that’s not exactly bullet proof. T&Cs can be rewritten and corporations with Morals? Right…