DotNet 6.0下SignalR跨域CORS错误问题求助

我注意到这个问题已被多次提及，但所有旧解决方案在DotNet 6.0环境下均无效。

我有部署在Server A的SignalR JS客户端，SignalR服务端部署在拥有固定IP的Server B，两台服务器均使用HTTPS。客户端连接服务端时出现CORS错误，提示：Error: Failed to complete negotiation with the server: Error。

客户端连接代码 #

socket= new signalR.HubConnectionBuilder()
    .withUrl("http://X.X.X.X/MyHub")
    .configureLogging(signalR.LogLevel.Information)
    .build();

服务端CORS配置（Server B的Program.cs） #

服务器为Ubuntu 20，Web服务基于ASP.NET C# 6.0开发，已配置CORS策略：

builder.Services.AddCors(options => options.AddPolicy("CorsPolicy", policyBuilder =>
{
    policyBuilder
            .AllowAnyMethod()
            .AllowAnyHeader()
            .AllowAnyOrigin()
            .SetIsOriginAllowed(_ => true); // allow any origin 
}));

Nginx配置 #

Upstream配置 #

upstream websocketCloud {
  server 127.0.0.1:9771;
}

CORS相关配置 #

# Wide-open CORS config for nginx
    location / {
    if ($request_method = 'OPTIONS') {
        add_header 'Access-Control-Allow-Origin' '*';
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
#
# Custom headers and headers various browsers *should* be OK with but aren't
#
        add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
#
# Tell client that this pre-flight info is valid for 20 days
#
        add_header 'Access-Control-Max-Age' 1728000;
        add_header 'Content-Type' 'text/plain; charset=utf-8';
        add_header 'Content-Length' 0;
        return 204;
    }
    if ($request_method = 'POST') {
        add_header 'Access-Control-Allow-Origin' '*' always;
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS' always;
        add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range' always;
        add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range' always;
    }
    if ($request_method = 'GET') {
        add_header 'Access-Control-Allow-Origin' '*' always;
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS' always;
        add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range' always;
        add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range' always;
    }
}

现寻求解决该跨域CORS错误的有效方案。

内容的提问来源于stack exchange，提问作者Andrew Simpson