I stuck with installing Toolchain Manager (and some other components) behind a Proxy from inside a newly installed nRF Connect SDK 4.4.0.
Unfortunately I do not know where and how to set "--detect-proxy" or HTTP_PROXY environment (see error message below).
The target of the link inside documentation sends me to a non existing page (404)
This is the error message
Unable to install downloadable app. Show technical details Error: Failed with exit code 1. Failed to bootstrap core functionality before executing command. HTTP request to default bootstrap resource raw.githubusercontent.com/.../ master/bootstrap.json failed. Please check that your internet connection is functioning. If you use a proxy, please try the --detect-proxy flag or manually set the appropriate HTTP_PROXY- style environment variable(s). To use a custom bootstrap config, set NRFUTIL_BOOTSTRAP_CONFIG_URL. To bootstrap directly from a nrfutil-core package tarball, set NRFUTIL_BOOTSTRAP_TARBALL_PATH. Caused by: 0: error sending request for url (raw.githubusercontent.com/.../bootstrap.json): error trying to connect: proxy authentication required 1: error trying to connect: proxy authentication required 2: proxy authentication required.