Thank you for separating the 2 issues (sound and keyboard) into 2 different threads. It makes it easier to work this way.
This issue seems that for some reason the keyboard is not properly configured by the bios & grub to input at the stage where the luks password needs input.
Does the built-in keyboard work once the system has finished boot?
If it does then it may be something in the decryption process itself that is not recognizing the keyboard input.
I wonder if this may be related.
That is definitely tied to mac machines (including the macbook) with intel processors.