Open firmware only matters if the board lets you build and flash it. These are the mainboards and MCU chips behind printers and CNC — what's on them, how open they are, and the real way to compile and flash Klipper or Marlin onto each.
menuconfig, MCU choice, the bootloader-offset trap, and SD / DFU / BOOT0 flashing — the gotchas, learned the hard way.
The silent boards in millions of Enders — standard STM32F103/GD32, so open firmware runs. With the SD-flashing pitfalls.
The open upgrade boards — STM32, swappable drivers, documented, Klipper/Marlin by design. The enthusiast default.
Mainboard + SBC combo for an all-in-one Klipper host — the tidy modern build.
The Pi Pico chip as a Klipper MCU and CAN toolhead — cheap, capable, UF2-flashed.
A toolhead board on CAN bus — fewer gantry wires, the current high-end wiring trend.