Open-Source-Mouse based on an Arduino Pro Micro utilizing the PMW3389 sensor
Open-Source-Mouse based on an Arduino Pro Micro utilizing the PMW3389 sensor

GitHub - BenMakesEverything/PMW3389_Mouse: Code for a 3D printed Arduino Pro Micro mouse utilizing the PMW3389 sensor.

The project has nothing directly to do with Linux. But I think it's interesting and you should be able to use the mouse under Linux. In my opinion, it is therefore an alternative to normal mice.
other open source mice and trackballs:
ploopy: https://ploopy.co/
jfedor2: