In this fork have support to use CloudFlare bypass with POST requests.
For Get request:
using Leaf.xNet.Services.Cloudflare;
var httpRequest = new HttpRequest();
var clearResp = httpRequest.GetThroughCloudflare("https://...");
For POST request:
string postData = $"UserId={Login}&SessionInfo={token}&Password={Password}&.........";
var response = httpRequest.GetThroughCloudflare("https://...", HttpMethod.POST, postData);
If need bypass CloudFlare with POST request without "postData", in the parameters need send null or empty string.