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Yes, it is possible to get a compressed 'techsupport' file while the device has not onboarded yet. For the detailed steps, see Show TechSupport before Device Onboarding.
22) Does the EdgeView Client script run on MacOS and Window
Yes. the generated EdgeView client script will run on MacOS, assume the docker client has been installed on the MacOS. It will run also on Window OS if the Docker Desktop for Window and WSL 2 is installed (e.g. with Ubuntu distro).