After the whole Logitech "subscription mouse" junk I decided to see if there was an open hardware thumb trackball, and there is! I just built a Ploopy Thumb trackball, and the hardest part was soldering on the sensor. I even printed out my own orange buttons. I will mess with the firmware (QMK!) later this week.

Edit: link to kit: https://ploopy.co/shop/thumb-trackball-full-kit/