LOFT is free on macOS and remaps your laptop and standard keyboard into the thumb-keyed, split-layout, ergonomic dream you've been seeking!
It positions your hands up and out in a creative way to get you all the goodies you thought you'd need some garage-built, geek-contraption for. All on a standard ANSI keyboard.
Maybe of interest is that the site's keyboard graphics are all generated HTML+CSS via Hugo partials.