Browser is required to authenticate
When executing mdc auth the default browser on your operating system is expected to open, allowing you to authenticate to Metrics, via a log in or sign up.
If a browser is not installed or a default browser is not set, the authentication process fails and prevents further use of the DSim Cloud CLI (mdc).
Workaround
There is currently no workaround.
A browser must be installed and set as default.
macOS and Windows machines usually come with a default browser. Linux users should install their preferred browser and set it as default. There are many online articles explaining how to do this.