Hi Qole, thanks to you and rebhana for your efforts and getting understand the whole file extension/mime type shebang.
Tried the new version, glad to see that vlc is included by default as a handler, I'm sorry to say that rtsp association has stopped working

I get a window as if it is launching a program, but no banner to say which program is being launched. Stays that way for about 10 seconds then returns to the task menu.