There are probably some games that this would work well for, but I’m not sure that it’d be a great replacement the way a physical thumb keyboard is for texting or the like.

Most present-day games that I can think of that I play use the keyboard as a grid of buttons. They expect to have your hand over the thing – often the left hand, with the right on the mouse – to let you be able to push multiple buttons quickly.

I’m not usually doing much text entry, which is what I’d expect a thumb keyboard to work well with.