Could you share your platformio.ini
Btw. a little bit off topic:
I also tried some mbed samples: Simple programs without library work.
But when I use some libraries which works with the online compiler, they never worked with platformio.
Last sample I tried was:
TextLCD lcd(PA_9, PC_7, PB_5, PB_4, PB_10, PA_8); // it's an lcd-shield for arduino
I copied the TextLCD library into the lib folder,
which compiles and upload fine but did not work on the nucleo-f103rb board.
platform = ststm32
board = nucleo_f103rb
framework = mbed