OK. You are using the 'old' Roger Clarke core.
Here is a reasonable overview of the current situation regarding STM32 Arduino support . Program "blue pill" with STM32 Cores in Arduino IDE · One Transistor
Your compact board appears not to have Boot0 (physical pin 44) broken out so I am not sure how you work with the standard bootloader.
The ST-LINK V2 programmer clones are very cheap so may, in your case, be an option.