Directory raw.githubusercontent.com/home-assistant/supervis… returns "404 not found"
However raw.githubusercontent.com/home-assistant/supervis… does.
To make this work again one must change the curl command to
curl -Lo installer.sh https://raw.githubusercontent.com/home-assistant/supervised-installer/master/installer.sh
And edit the URL_RAW_BASE in installer.sh
URL_RAW_BASE="raw.githubusercontent.com/home-assistant/supervis…
While I was in there I also removed the problematic NetworkManager snippet (the couple of lines below # Create config for NetworkManager)