According to this https://android-developers.googleblog.com/2017/03/update-your-app-to-take-advantage-of.html
I need to set max_aspect. There is still no S8 device for the emulator so I set the 5.8" with 2960 x 1440 resolution in the hardware profile. My app looks OK, without setting the maz_aspect, it fills the screen without black lines as shown in the google article.
How can I test the new 2.1 ration?