New Twiddle

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
}

select.component\.js

import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';

export default class extends Component {
  @tracked selected = 'OR';
  
  @tracked firstState = 'CA';
  @tracked secondState = 'OR';

  options = ['CA', 'OR'];
}

select.template\.hbs

<h1>Works</h1>
<select>
  {{#each this.options as |opt|}}
    <option value={{opt}} selected={{eq opt this.selected}}> {{opt}}</option>
  {{/each}}
</select>

<select>
  <option value={{this.firstState}} selected>{{this.firstState}}</option>
  <option value={{this.secondState}}>{{this.secondState}}</option>
</select>

<h1>Broken</h1>
<select>
  {{#each this.options as |opt|}}
    <option value={{opt}} selected={{eq opt this.selected}}>
    	{{opt}}
    </option>
  {{/each}}
</select>

<select>
  <option value={{this.firstState}} selected>
    {{this.firstState}}
  </option>
  <option value={{this.secondState}}>
  	{{this.secondState}}
  </option>
</select>

templates.application\.hbs

<Select/>

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",
    "ember-truth-helpers": "2.1.0"
  }
}