Final thoughts, Chrome will not work at all unless I manually put in an exception, it also doesn't like the frame, the final site being http://websiterni.zapto.org/355/ListenPage.htm

So I would either ditch the frame and link to zapto directly and get an SSL cert or keep the content on http://355.vze.com/ListenPage.htm without a frame and get a cert for that, with most providers you just tick the SSL box and you get a free LetsEncrypt cert.

Unfortunately these SSL issues are only going to get worse, even Firefox is saying temporary exception, so it will time out at some point. The trouble is most people now are going to see the first warning page and go no further, and with Chrome you can't anyway without putting an exception in.

Anyway I copied your stream URL's into VLC so that's not a problem, there's an extension for Chrome and Firefox to open streams directly in VLC, so I think that may solve the other https problem with the streams.