New Twiddle

controllers.a\.js

import Controller from '@ember/controller';

export default Controller.extend({
  queryParams: ['qp'],
  qp: 'qp_default_value'
});

controllers.application\.js

import Controller from '@ember/controller';
import { computed } from '@ember/object';
import { inject as service } from '@ember/service';

export default Controller.extend({
  router: service(),
  
  isActive_a: computed('router.currentRoute', function() {
    return this.router.isActive('a');
  }),
  
  isActive_a_qp_default_value: computed('router.currentRoute', function() {
    return this.router.isActive('a', { queryParams: { qp: 'qp_default_value' } });
  }),
  
  isActive_a_foo: computed('router.currentRoute', function() {
    return this.router.isActive('a', { queryParams: { qp: 'foo' } });
  }),
});

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('a');
});

export default Router;

templates.application\.hbs

<LinkTo @route="index">Go to /</LinkTo>
<LinkTo @route="a">Go to /a</LinkTo>
<LinkTo @route="a" @query={{hash qp="qp_default_value"}}>Go to /a?qp=qp_default_value</LinkTo>
<LinkTo @route="a" @query={{hash qp="foo"}}>Go to /a?qp=foo</LinkTo>

<p>isActive(a) == <output>{{isActive_a}}</output></p>
<p>isActive(a?qp=qp_default_value) == <output>{{isActive_a_qp_default_value}}</output></p>
<p>isActive(a?qp=foo) == <output>{{isActive_a_foo}}</output></p>

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"
  }
}