The most common "best" firmware options for the Sapphire Pro are Klipper and Marlin. Klipper: The High-Performance Choice

Look for repositories like the Mks-Robin-Nano-Marlin2.0-Firmware-for-Sapphire-pro which supports the colorful LVGL GUI and touch screen interface.

Look at your green mainboard. Does it say "Robin Nano V1.2" or "Robin Nano V1.3"?

The best firmware for tinkerers and remote printing . If you hate recompiling Marlin, get Klipper.