discourse/app/assets/javascripts/admin/addon/routes/admin-user-fields.js

import DiscourseRoute from "discourse/routes/discourse";
import UserField from "admin/models/user-field";

export default DiscourseRoute.extend({
  model() {
    return this.store.findAll("user-field");
  },

  setupController(controller, model) {
    controller.setProperties({ model, fieldTypes: UserField.fieldTypes() });
  },
});