Development tools for Zephyr on STM32Workbench 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.
Your're spot on there, Sylvain.
That reference in the plugins folder (stm32fxx.cfg) overrides the one in the custom.cfg in the workspace -> I had same problem on different device.
Fixed it