Ethernet interface problem on stm32f407

It seems there is an issue with online compiler. So I’d suggest to import this demo project into the Mbed StudioIDE and build it offline for the ARCH_MAX target using Mbed OS 6.4.0. It worked fine for me.
Please notice that it prints to UART1 (pins PA_9, PA_10) available on the UART header next to the JTAG/SWD header .