@model bug

components.person\.js

import Component from '@glimmer/component';

export default class extends Component {
  willDestroy() {
    // this.args.person here is missing when it is called as a result of transitioning to another route
    console.log({ person: this.args.person });
  }
}

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('some-other-route');
});

export default Router;

routes.index\.js

import Route from '@ember/routing/route';

export default class IndexRoute extends Route {
  model() {
    return {
      firstName: 'Little',
      lastName: 'Sebastian'
    };
  }
}

templates.application\.hbs

<div style="margin-bottom: 2rem;">
  <LinkTo @route="index" style="margin-right: 2rem;">
    Index
  </LinkTo>
  <LinkTo @route="some-other-route">
    Link to other route
  </LinkTo>
</div>

{{outlet}}

templates.components.person\.hbs

<div style="border: 1px solid red;">
  <p>{{@person.firstName}} {{@person.lastName}}</p>
</div>

templates.index\.hbs

<Person @person={{@model}} />

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"
  }
}