I've created a simple Mbed OS project and imported it into Keil Studio.
The following simple line produces no output in the serial terminal:
Hi Nicholas Outram,Apologies for the late reply. Serial isn't currently supported for ST devices within Keil Studio Cloud. We're currently working on implementing this.In the meantime, please refer to our documentation on how to use an external serial monitoring program: https://developer.arm.com/documentation/102497/1-5/Monitor-and-debug/Use-the-Serial-Monitor-view/Use-an-external-serial-terminal-with-STMicroelectronics-devicesHope that helps.Kind regards,Carey - Studio Team