Why doesn't a Confluence theme work?

So I have set up my ACE development environment, put a confluenceThemes example into the modules section of atlassian-connect.json, installed ngrok etc etc, and started it via npm start.

After what it feels like two hours, I get the /installed POST request, it pulls the icon, I go to the dev site, install the theme (tried global and space), but NOTHING. All default colors.

Am I missing something? Doesn’t this work anymore?

Could it be this?

The Theme API was built for a UI that Confluence has recently moved away from, and doesn’t support the new UI. Based on Theme API usage to date, we are evaluating whether Theme API will support the new UI.


It probably doesn’t work.

The example screenshots here look very old.

Everything around developing within the Atlassian ecosystem is just so incredibly sad.