I've designed a custom STM32-based board but one can use a STM's Nucleo development board as well. Bus-coupling interface is quite simple because of STM32's built-in DAC (threshold voltage for pulse detection) connected to built-in comparator (comparing threshold voltage with bus voltage) that triggers a timer. The rest of the processing is pure selfbus.
My version is compatible with Arduino so one can write a single .ino file and compile the firmware from Arduino IDE or VS Code.
See my Hackaday.io project log, Project GitHub page with schematics etc. and Library GitHub page.
I also plan to improve the "OTA" firmware updating - send only a diff between old and new firmware, allow to activate bootloader after device (bus) reset by sending a magic telegram instead of triggering the physical prog button (which will also work).
Any comments and pull requests are welcome
