Perhaps the keyboard could have an internal speaker that provides carefully crafted additional noise to make the keys sound more uniform (like each-other), or t

Perhaps the keyboard could have an internal speaker that provides carefully crafted additional noise to make the keys sound more uniform (like each-other), or to sound more random (different each time). However, if the counter-noise would get triggered first by a key press then it would not be able to mask the initial part of the key noise when the finger strikes the key surface before pressing it down. Detection using a microphone would have the risk of false positives, so maybe a new key mechanism also including capacitive touch/proximity sensors would be needed. And it would be ineffective against attacks that model key stroke patterns temporally.