For those of you with Sony Displays, this may come in handy regarding the Shield's lack of HDR for both Youtube and Google Play movies due to the device not having the VP9 Profile 2 Spec.
I was off for the past 5 days, and during this time I discovered that I can get a "Somewhat" HDR look for some Youtube Videos. Either they are filmed in 4K, or they are videos that are well put together, no matter the resolution.
There are three areas in your display's menu you'll need to make adjustments.
Specifically for the X900E models: Brightness Settings, Picture Mode, and Motion settings.
I have a Off-White wall with a Phillips Hue Light Strip attached to the back of my Display to improved contrast performance.
For Picture Mode, set your display to "Cinema Pro". This will add some contrast to your image, plus increase the "whites" as well.
For Brightness settings, for non-HDR content, I leave my Brightness at 20, Contrast at 85, Gamma at 0, and Black Level between 47 and 52.
For motion, set Clearness to "Min".
Look for a 4K video (does not need to be in HDR) with a lot of lights, for example, there are tons of 4K Car videos available in which you can test out your displays settings.
Within the video I posted (for example) look for instances of the Audi driving at night and focus on the headlights.
Getting Back to the Brightness settings, Advanced Local Dimming along with X-Tended Dynamic Range are important. You cannot adjust X-Tended Dynamic Range while Advanced Local Dimming is disabled, so keep that particular setting enabled.
I keep my Advanced Local Dimming to its Maximum Level. If you enabled X-Tended Dynamic Range to just the minimum level, then disable it after 5 seconds, you will noticed that Specular Highlights will go from a pinpoint brightness, to almost washed out.
Also within the Brightness menu, you can make adjustments to the Black Adjust and Advanced Contrast Enhancer settings as well.
I noticed a much improved image by making these adjustments. Unfortunately, said adjustments may do not fair well with other videos. I pulled up an old clip from the TV series "Motor Week" and the host, John Davis, looked as if he had an extreme tan. Also, some videos will make white reflections and backgrounds completely washed out. By simply disabling X-Tended Dynamic Range within the Brightness settings, this improved that aspect of some of the videos I streamed.
Again, this is just experimental, not a permanent fix. If you have other means to view HDR content within youtube such as your Sony TV's native Youtube app, or a Chromecast Ultra, then by all means keep using them.