If you ask “Alexa, show me [query] videos,” the Echo Show will display a list of videos matching your search using Bing. The results will be a mixture of YouTube, Vimeo, and Dailymotion videos. Selecting a video, either by tapping it on the screen or by saying “Play number [#],” will open what looks like the standard mobile webpage for the video service.
Prior to Google blocking the Echo Show’s access to YouTube, selecting a video on the device would begin playing the video in full screen. The new interface is much worse for a voice-first device like the Echo Show, but it’s the only way Google will allow access to YouTube videos.
When asking for videos, you can add “…from YouTube/Vimeo/Dailymotion” to the end of your request to limit results from a specific video service. Additionally, you can say “Alexa, play [query] videos” to start playing the first video that the search brings up, instead of seeing a list of videos. Amazon says that more video services will be added over time.