How to build android game with 18.5:9 ratio?

In my Unity I’ve been working on a game set to the 18.5:9 ratio (actually 18:37 in the game scale due to no decimals)
On the player settings for android there is no option for aspect ratio or resolution other than resolution scaling which doesn’t really seem to do anything.

Does anyone know how I can build this game to support Galaxy S8 Ratio?

Not sure what kind of game you’re building but if you build it using the UI Canvas with images and buttons then the game will automatically scale depending on the device resolution, providing you set up the right properties:
https://docs.unity3d.com/Manual/HOWTO-UIMultiResolution.html