Modifier on LinkTo

controllers.index\.js

import Controller from '@ember/controller';
import { action } from '@ember/object';

export default class ApplicationController extends Controller {
  @action alert() {
    alert('Action happened'); 
  }
}

router\.js

import EmberRouter from '@ember/routing/router';
import config from './config/environment';

const Router = EmberRouter.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('foo');
});

export default Router;

templates.application\.hbs

<h1>Welcome to</h1>
{{outlet}}
<br>
<br>

templates.foo\.hbs

<h2>Foo</h2>

<LinkTo
  @route="index"
>
  Link back to `index` without extra action on it
</LinkTo>

templates.index\.hbs

<h2>Index</h2>

<LinkTo
  @route="foo"
  {{on "click" this.alert}}
>
  Link to `foo` route with `&lbrace;&lbrace;on "click" this.alert}}` on it
</LinkTo>
  

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}