Topic: Smart TVs, smart devices, and TV apps
When opening YouTube the cast icon that pops up is enabled by a technology called DIAL. It is basically the foundation of the Chromecast protocol but DUAL was abandoned when Google decided to take it in as its own. DIAL should also work with Netflix from a mobile device but functionality is very limited.

I don't think DLNA is a good solution if you want to use this on a daily basis. If you want the ability to cast video from a PC I suggest that you invest in a Chromecast dongle.