How to output SWO trace?
To ansver myself, I followed these instructions (and ditched the custon .cfg file) and everything was OK.
http://alphaloewe.com/2017/01/24/enable-semi-hosting-with-openstm32-system-workbench/
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Development tools for Zephyr on STM32
Workbench for Zephyr: VS Code extension to set up, build, flash and debug Zephyr applications on STM32.
Devicetree manager: browse, edit and visualize Zephyr devicetree, STM32CubeMX-like for Zephyr.