Related: #2358

Enable the Unsupported Block Editor on WordPress.com sites where the default editor is the Classic editor.

The missing feature

On WordPress.com sites, the Unsupported Block Editor should always be available, even if Gutenberg is not the default editor. Users may have existing posts they wish to edit that were made with Gutenberg, but their site has the Classic editor enabled as the default editor.

Alternatives

• We could leave things as-is, and the Unsupported Block Editor will only work on sites where Gutenberg is made the default editor. Intuitively, it seems that most users wishing to edit an unsupported Gutenberg block will have Gutenberg enabled as their site's default editor.