USB Serial for Blue Pill (STM32) with PlatformIO - Donney Fan
Program Blue Pill STM32 directly with USB port - IoT for Geeks
GitHub - DAlexis/stm32-usb-bootloader: This repository contains bootloader for stm32f1xx microcontrollers. It works for stm32f103ret6, but you can simply adopt it to any MCU supporting STM32 HAL library with USB and SD-card
STM32 Blue Pill USB Bootloader — How I fixed the USB Storage, Serial, DFU and WebUSB interfaces
Programming an STM32F103 board using its USB port (Blue Pill) | by Param Aggarwal | Medium
Program Blue Pill STM32 directly with USB port - IoT for Geeks
2016 CC3D REVO board and bootloader - Arduino for STM32