I used a ksger station flashed with the great firmware(stm32_soldering_iron_controller) for several years and really liked it. I recently ordered 2 more sold as the same HW version, not even close.

Disappointed I figured out that all the makers of these are constantly changing them. So I designed my own. It was designed to be compatible with the above firmware for ksger V3. It uses a bucking power supply to convert 24V to 5V and then a 3.3V LDO to solve the heat issues some had with just a linear supply. A real STM32. It has snip-able jumpers to chose between the cold side NTC being in the handle, or one on the control PCB since newer handles don't include it. Personally I add the NTC to the handle. Battery works for storing last settings for power up, something else that was cheapened. Snipping the end of the board off where the iron connector is allows it to replace other brands control boards with leads.