Why am I asked to open YouTube videos in VLC? I use the mobile site for YouTube in safari on iOS 13.3. Sometimes when I tap play on a video I get a pop up saying 'Open in "VLC"?' as though I had ever made the slightest indication of wanting that. 

When I tap cancel I'm left with a non playing video in safari.

How do I disable this nonsense? What's causing it? Is VLC now affiliated with YouTube, or if not, how do I prevent it from infiltrating the domain and interfering with my browsing?
This is most probably caused by having played around with &quot;Request Desktop Site&quot; in Safari, whereby I somehow end up getting served a mobile page, but with an unsupported video format (likely VP9).