I've assembled rev 4.0, the version with the newest STM32U385 chip and 49-key keyboard. As usual, all the design files are available on OpenRPNCalc github.

The firmware is mostly the same for now, just adapted to the new MCU chip and with minimal modifications to the keyboard layout to use 49 keys. However, with the hardware improvements (USB-C, flash and a more powerful MCU), we can aim to eventually support DB48x firmware.

Welcome jcordona on board, he is trying to build rev 4.0 with third-party PCB assembly. If anybody else is brave enough to join this effort, welcome to the github discussion thread.