No, you can't analyze a video from Youtube or any other video platform with the URL of the video. 

When selecting the "Camera IP" option, is for an IP Camera device, and the URL is the one to connect with that camera. If you try to enter a Youtube video link here, you will have the following error: 

"The following error happened and the current capture will be closed:
Your GStreamer installation is missing a plug-in."

If you want to analyze a video from a video platform, you can either download the video and analyze it as a normal video file, or if you have two monitors in your computer, you can just create a Capture Device project and in the list of devices you will find your monitors and you can capture your screen while working on LongoMatch in the other one: