Still haven't had a chance to rebuild the kernel. However, since we're on 5.11, I followed danb's suggestion to add i8042.reset=1 to grub. And it took care of having to warm boot to login. So thanks for that one. Touchpad is not fully functional yet (no right click and no num pad), but...
I have this problem as well with new ASUS Zenbook UM425UA and Linux Mint Mate 20.2. I upgraded the kernel to 5.11.0-27, which fixed other things, but not this. Also reinstalling xserver-xorg didn't do it. Touchpad and external mouse work fine. Just no keyboard on cold boot. So everytime we...