Introducing cookieless authentication beta with App Bridge

Can Shopify provide better support for Python / Django? I find it hard to implment the new authentication on my own.

Now, I can only render a page with App Bridge setup. When I clicked Test app on development store => select my development store, it shows

  1. My test page with App Bridge under my URL. (Load skeleton like the doc said?)
  2. App Bridge force redirects me to Shopify admin (cannot create app with App Bridge here since the origins are unmatched)
  3. It redirects to https://mystore.com/admin/apps/appID/login/?hmac=a668c39fd49ca4ff80ce38dee3ae213072270ce8250188e9605d73c4f831b89e&shop=mystore.com&timestamp=1600686416 and gives 404, where [login] is the handle to my app url
  4. Stop here

I don’t know how to go further. I suppose to load App Bridge in Shopify admin and get my session token with getSessionToken(App)

How can I go further?