Debug EVK1000 over ST-LINK?

Dear all,
I’m currently using one of the 4 boards inside TREK1000 system. I have all the tools needed to write custom firmware (STM32CubeIDE, ST-LINK v2) and I manage to write simple programs and run on board. Is there a way to print some information, for example with printf(), over JTAG connector? My idea is that UART cannot be used because there is no physical connection: I tried to write some information using USB function, CDC_Transmit_FS(), but it always return me USBD_BUSY. Is there a simpler way using ST_LINK JTAG Interface, or do I have to solder some pins using then a UART-USB connector?
Thanks to everyone,