Vionixon Stack Overflow • Recommends
On “How to scale unity UI for every device”
…or width. For example a portrait game will scale only by height if you switch from 9:16 to 9:18.(0.5 has worked always for me)
Select the aspect ratio in the game window and set the Anchors of the UI to the corner of the UI element. That way Unity will know where the element should be based on Canvas size.
Here is a video that demonstrates it
link to this video…