Before you can use Feathermost, the admin of your Mattermost servers must set up CORS appropriately. If this is not possible, you can use a CORS puncturing proxy, such as the mitmproxy setup provided for development (see below).
To run in development mode, execute
This will start a web server, and mitmproxy to avoid CORS problems.
Dependencies for that: Bash, Python and
Then open http://localhost:8000/ in your browser.