Screen stretch

Hi all,

I am delevoping a 3d game for Android. I am designing it to work on a 16:9 aspect ratio preferably working in 1920x1080. This is fine but when I test it on my Galaxy Note 9 which has a 18.5:9 aspect ratio I get to see more of the 3d environment, which I don't want. I don't want to have to build the environment any bigger than it is already.

I have included a rough image to illustrate

The green area is the game level. The black screen is what I can see on a 16:9 aspect screen which doesn't show anything beyond the level. The red box is what I see on my Note 9.

This has probably been answered many times before but I cont seem to find the anything which refers to what I am after. All answers are for scaling the UI. Is there any way I can either just squash or stretch the screen to fit different aspect ratios or show black borders?

Any help or suggestions are greatly appreciated.

Thanks in advance.