I got the Ti-99/4A as a bday gift in '83.Then within a few months Texas Instruments discontinued it. I still have it in a box somewhere. Been kicking around some ideas. Maybe remove the mainboard and put in a RaspberryPi 4 or some other SBC. Then wire it up to the keyboard. Someone was selling a board on tindie that made it possible to connect the keyboard ribbon cable to USB. But sadly its no longer being sold.