If you are using a digital copy or an NSP (Nintendo Submission Package) for custom firmware, the patch (approx. 450MB) is essential. Here is the changelog based on datamines and developer notes:
To verify and update your legitimate copy directly through Nintendo: Highlight the icon on your HOME Menu. Press the + button on your controller. omori switch nsp update eshop verified
The OMORI Switch NSP update promises to deliver a seamless gaming experience, with several key features: If you are using a digital copy or
OMORI Switch NSP Update Live on eShop - Verified Press the + button on your controller
feature. By connecting with their friend’s physical copy, their digital version updated instantly, bypassing the wait. A Warning About NSPs
The Switch (and other console) versions include extra content not found in the original PC release, such as new photos for the photo album and expanded boss rush options in specific routes.