A highly amusing reality with ARM MCUs is that they have different and often incompatible peripherals, mapped to highly different areas in the memory space. Worst of all here are timer peripherals, which come in a variety of complexities, with them in general being able to generate any desired output signal on a GPIO pin, including PWM, as well as work as interrupt-based timers to control the execution of the firmware.
Configuring timer peripherals and similar complex peripherals isn't for the fainthearted. Similarly, using a built-in MAC with an external PHY (Ethernet physical interface) requires a lot of in-depth knowledge to know how to configure them. Reading the datasheets and application notes is essential here.
Relying on autogenerated code by tools such as ST's CubeMX software for their STM32 range of ARM MCUs can lead to you...
