Expected behavior

In Reader, when viewing a private site that uses a mapped domain (e.g. example.com, not example.wordpress.com), tapping Visit to view the site's posts in a web view should load the site and log the user into the site automatically.

Actual behavior

In Reader, when viewing a private site that uses a mapped domain, tapping Visit to view the site's posts in a web view results in a page that doesn't load.

For private Simple WP.com sites with mapped domains, I get a "Protected Blog" screen.
For private Atomic WP.com sites with mapped domains, I get a "This site is private" screen.

Screen recording

Steps to reproduce the behavior

1. Open Reader
2. Filter the site list to show posts from one of the two site types affected by this bug
3. Under the Following tab:

• Tap the ellipsis menu (°°°) on a post → Visit
• Tap the site title on the cell → on the new screen tap the ellipsis menu (°°°) on a post → Visit
• Tap the post title on the cell → on the new screen tap the ellipsis menu (°°°) → Visit

4. Notice the "Protected Blog" or "This site is private" error screens

Additional information

• First reported in Issues/15266 fix preview url #15309 (review)

Tested on iPhone 11, iOS 14, WPiOS 8e71775 (which will land in WPiOS 16.3)