This question already has an answer here:
I currently having an unused keyboard (a HP's KBRF1921 to be exact). I always need to type some Greek characters such as αβɣ and latin character as abc.
It'd be great if I could use one for latin and map another one for Greek. Having go to charmap or insert symbol everytime i want to type them is somewhat annoying all the times. There's already one asked here: How can I use a second USB keyboard for special keys under Linux? but the question is not currently answered yet and it's narrow for linux only and usb. My current keyboard uses PS/2 in order to save off some USB ports. And there's another one here: https://steamcommunity.com/app/238460/discussions/1/540741859026417095/ but their solution is for games.
I'm using both Linux and Windows so what applies for either platform is welcome.