Resolved! Blackpill STM32F411CU6 lacking SWO Pin in SWD header => no SWV ITM printf ?
All clock setup and tracing enable checkbox checked and port0 selected but still no SWO printf debug messages in CubeIDE debugger. Further research led to the SWO pin function (PB3) that deliveres the trace data from the board to the debugger. Howev...