I'm using the nRF Connect extension for VS Code and running into an issue with Sysbuild where calls to cmake for building the app image and the MCUboot image will use different python interpreters, there is discussion of this same problem on the zephyr-nix repo as well: https://github.com/nix-community/zephyr-nix/issues/48).
I've had success overcoming this issue by setting the PATH variable in the workspace setting...