What do you think about this?
https://danluu.com/keyboard-latency/ (https://danluu.com/keyboard-latency/)
for russian language: https://habr.com/post/345776/ (https://habr.com/post/345776/)
Unsurprising. Newer or more complex isn't always better. ;)
Also has a follow-up of sorts:
https://danluu.com/input-lag/ (https://danluu.com/input-lag/)