I have submitted a Ruby on Rails app for review some days ago but it has been rejected.
Your app must first authenticate into the merchant's store using OAuth from the 'Add App' button. Instead I am redirected to this page after trying to install the app. Please watch this example of what the required installation flowlooks like with OAuth when clicking 'Add App' from the App Store listing. An app should never ask the merchant for their .myshopify.com URL. If your app requires an account, the merchant should be able to create an account or sign in with an existing account after the OAuth process.
However, following any official tutorials, this step is always present. Merchant always enter their .myshopify;com.
Have you faced this issue before? Any idea of how to fix this? So that merchant will be land directly on permission page without entering their .myshopify.com?
Note: app is developed using Ruby on Rails
The app installation URL should have the OAuth step as the first step during installation, no intermediary screens. If the customer is logged into Shopify then, assuming the authorization goes just fine, Shopify is going to redirect them to the permission page. If the customer is not logged in, Shopify will ask them to login first and then proceed.
In your case you have your own screen where you ask the merchant to enter their shopify store id. It's perfectly fine if for example you have a site for your app and you want the customers to initiate the install from your site, so you can ask for their store id and then build the OAuth URL and redirect to it so Shopify can handle the rest of the flow.