ReadOnly demo

controllers.application\.js

import Controller from '@ember/controller';

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

templates.application\.hbs

<h1>Readonly Surprise</h1>
<br>
readonly=
{{ui-radio value=true current=checkReadOnly onChange=(action (mut checkReadOnly)) label="true"}}
{{ui-radio value=false current=checkReadOnly onChange=(action (mut checkReadOnly)) label="false"}}
{{ui-radio value=null current=checkReadOnly onChange=(action (mut checkReadOnly)) label="null"}}
<br>
<br>
{{ui-checkbox readonly=checkReadOnly label="Check me"}}

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": "3.8.3",
    "ember-template-compiler": "3.8.3",
    "ember-testing": "3.8.3",
    "semantic-ui": "2.4.1"
  },
  "addons": {
    "semantic-ui-ember": "3.0.4"
  }
}