The blue pill board has to be programmed once using an STM32 programmer. After that, you can use most standard Forth words and also use some that can manipulate the low-level microcontroller ...

I recently set out to use one of the cheap “blue pill” STM32 ... even the cheapest arduino clones, The STM32 Arm USD $1.70 ... There are LOTS of Chinese STM32 boards, all with different pinouts.