with the pro mini the project complies with E.G:Serial.begin and SPI.begin, however with the STM32 the project will not compile with Serial.begin , you need to define which port E.G: Serial1.begin.
Bullshit, the following sketch compiles fine for Arduino Mini and for a STM32F103 Bluepill.
#include <SPI.h>
void setup() {
SPI.begin();
Serial.begin(9600);
}
void loop() {
}