我能做些什么来解决这个问题(除了安装真正的 SSL 证书).

What I can do to fix this (other than installing a real SSL certificate).

你不能.

在https网页上，你只能向https网页发出AJAX请求(使用浏览器信任的证书，如果你使用自签名的，它对你的访问者不起作用)

On an https webpage you can only make AJAX request to https webpage (With a certificate trusted by the browser, if you use a self-signed one, it will not work for your visitors)