For a while now, my Hisense Roku 4KTV couldn't handle HDR correctly in streaming apps. The color space was always really dim and whites would display as gray. This was just for streaming apps - anything connected via HDMI, like my UHD player, would display just fine.
Well, I just got the OS 14 update and they've finally fixed the issue with streaming apps. Now my 4K library on Vudu can be watched just fine, along with any HDR content on the other streaming apps.
So happy this has been fixed! Just wanted to share for anyone who was also having the HDR issue with streaming apps.