Here is some information for users who already backed the game on Kickstarter:
If you’ve already pledged for a digital copy, but now want the Switch version, there’s no need to change anything! We will send out surveys closer to release to make sure that everyone gets the game on the platform of their choice.
If you’ve already pledged for a physical copy for PS4, but now want the Switch physical copy, you can change your tier by clicking the “Manage My Pledge” button. This is necessary because there are limited copies available for the physical editions on both platforms.
For those of you who have backed at the “Gaze of the Ninja” or “Enemy of the Ninja” tiers, we will make sure you get the physical edition on your platform of choice! We cannot edit those tiers since there are already existing backers.
Read more about the game here.