How to make my Landscape Orientation game also work with Portrait Orientation seamlessly?

Hello, I made a 3D WebGL game on Unity in landscape orientation (16:9).

I would now like to port this game to mobile and have it run in portrait mode. I would appreciate any ideas on how to make my game appear properly in portrait so that the screen contains all of the same stuff that it did in landscape mode without having to manually redesign my entire game around a portrait orientation (my code heavily relies on game object sizes).

I have tried messing with the field of view property on my camera but that isn’t working as intended. To put it in perspective, I could achieve my intended result if I was able to expand ONLY the horizontal FOV of my camera.