Keep keyboard open when lost focus by clicking background canvas - TextMeshPro Input Field

I have a form that contains a few input fields. I want to scroll down the UI while the keyboard is open. UI has a canvas and it's scrollable. But when I touch the canvas while the keyboard open, the keyboard will close due to lost focus. I found a few related questions but can't achieve this. If anyone knows how to achieve this behaviour, please help me.
I'm using TextMeshPro input fields
Platform - Android and iOS. @alnovlucky