Getting a fully assembled PCB can be expensive and will almost certainly have some issues, so I designed a small test board to replace the BlackPill version as it had limited GPIO's with an STM32F411 LQFP64 package.

The board is 72x32mm and contains all the electronics. Connection to the keyboard is via the 30 pin connector (1.27mm pin pitch). I've included level shift for RGB, rotary encoder (Volume etc.)... I'm almost certain I forgot something important...  See for more information on this Test Board.