Just because Stimulus.js is designed to work primarily with existing HTML doesn’t mean it can’t use JSON APIs when the need arises.
Here, John pimps up his Stimulus controller to get and use JSON from a remote API endpoint.
He triggers a fetch() from the connect() lifecycle callback, then iterates the returned JSON creating each HTML list item using a JavaScript template literal before finally rendering them into an existing <ul> via a Stimulus target.
Easy when you know how!