A simple program to fix doubled key presses on macOS using just software.
Download this GitHub repo, cd to its folder in Terminal, and then run make in Terminal to build it. Then run sudo make install in Terminal to install it. Your password may be required.
Run untap in Terminal. By default, it will ignore keypresses within a millisecond of each other. You can change this amount by running Untap with arguments. Examples:
untap 1000 # 1 millisecond (the number is in microseconds)
untap 10000 # 10 milliseconds
untap 1000000 # 1 second (I don't recommend such a high number)