Your Own Hardware: Using KiCAD to Design a Minimal STM32 Development Board – Vivonomicon's Blog
PCB-STM32-F3U | STMicro Discovery-F3 UEXT BaseBoard | BusBoard Prototype Systems
OnStep STM32 Blue Pill - EasyEDA open source hardware lab
PCB-STM32-VLB1 | STMicro Discovery-VL BaseBoard | BusBoard Prototype Systems
GitHub - DanielMartensson/STM32-PLC: STM32 microcontroller with lots of periferials such as ADC, differential ADC, Input Capture, PWM, USB, Encoder, DAC, Digital Input, RTC, CAN-bus + Alarm etc.