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.
That's my hunch as well. I'll be taking the laptop home tonight and trying it over my ISP connection and will let you know - I'd say don't spend any more time on this until I can do that.
Thanks,
DT