If you are using Windows 10 right out of the box (without customizing settings) there shouldn’t be any real reason why videos would not work on Edge. There could be some odd firewall issue you may be experiencing but if it is a browser issue, have you tried
using a different browser or even tried opening the page in IE? Are you also experiencing these problems in the apps as well?
WatchESPN uses flash (http://espn.go.com/watchespn/faq#faq40) and according to your comment you have already ensured flash was working for you in Edge. Your symptoms for WatchESPN suggest that either you or your TV provider does not have access to certain
ESPN content such as live stream or, well, anything worth watching...
YouTube and Netflix both use HTML5, although Netflix can also use Silverlight (https://help.netflix.com/en/node/23742). You could try visiting https://www.youtube.com/html5 to see if HTML5 is supported by your current browser settings. If the page says
that HTML5 is not currently supported by your browser you can try the following;
Right-click on your start menu > Select ‘Control Panel’ > Click ‘Network and Internet’ > Click ‘Internet Options’ > Go to the ‘Advanced’ tab > Scroll down to the ‘Multimedia’ section > ensure ‘Enable alternative codecs in HTML5 media elements’ is checked.
Hopefully this helps.