I'm pretty sure keyboard works out of the box, because during playtesting, keyboard movement still works. You just need an OTG cable to connect the keyboard, or connect the keyboard to bluetooth before opening the game.
Viewing post in Baldi's Basics for Google Cardboard comments
Hey! Thank you for the response!
I tried connecting my wireless keyboard through Bluetooth before opening the game, but it doesn't work in-game. The keyboard works normally on my phone, so I think the game may not be detecting Bluetooth keyboard input.
Could you possibly add or test support for Bluetooth keyboards? It would be really useful for VR Cardboard users who want to play without needing an OTG cable.