Development installation has no addon option

Development
1

Followed the developer instruction to manually install HA from GitHub - home-assistant/core: 🏡 Open source home automation that puts local control and privacy first. dev branch.
It seems to work fine when I start it and log in to UI.
I want to install MQTT addon with a view to creating a component for the energy dashboard.
Every instruction I can find says " navigate to the add-on store using [Settings > Add-ons > Add-on Store]in the UI" which does not exist on the setting page.
This URL Link to Add-on store – My Home Assistant tells me " It needs either the Home Assistant Operating System or Home Assistant Supervised installation method"
So I’m assuming what ever that problem is it is the same reason there is no addon option on the settings page.

How can I install the Mosquitto addon when every instruction says to use the settings/addon UI that doesn’t exist?

2

You don’t need an addon specifically to do development. You can just install Mosquitto on your own, and then connect to it with the MQTT integration.

Addons are nice for convenience but they don’t allow you to do anything that you couldn’t otherwise install in a different way.

If you’re running core, you are responsible for your own external software.