I have solved the keyboard problem in a different way: on a HP laptop with ubuntu 20.04 i had an external (USB) keyboard, and also a USB mouse. All integrated and external keyboards and mouse were working for long time. One day i connected another device (a monitor) to a USB port, apparently after that the external keyboard stopped working while the external mouse kept working. I tried two solutions in this page ("/etc/modprobe.d/blacklist-intel_vbtn.conf" and "slow keys") but did not solve the problem. I swapped the USB ports for keyboard and mouse, restarted the computer, and everything started to work fine again