rails new -n a11yist -d sqlite3 --skip-action-mailbox --css bootstrap --js esbuild .

app/javascript/controllers/application.js

@@ -0,0 +1,9 @@
+import { Application } from "@hotwired/stimulus"
+
+const application = Application.start()
+
+// Configure Stimulus development experience
+application.debug = false
+window.Stimulus   = application
+
+export { application }

app/javascript/controllers/hello_controller.js

@@ -0,0 +1,7 @@
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  connect() {
+    this.element.textContent = "Hello World!"
+  }
+}

app/javascript/controllers/index.js

@@ -0,0 +1,8 @@
+// This file is auto-generated by ./bin/rails stimulus:manifest:update
+// Run that command whenever you add a new controller or create them with
+// ./bin/rails generate stimulus controllerName
+
+import { application } from "./application"
+
+import HelloController from "./hello_controller"
+application.register("hello", HelloController)