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.
ok, se solved it ourselves: the boot0 pin was not pulled low by hardware, this caused that it always ran the bootloader when not debugging.
thanks though 😉