From Mobile First Indexing to Mobile Only Indexing

During the Pubcon (virtual) 2020, Google’s John Muller announced that “Content only visible on desktop will be ignored” starting March 2021. It means that if you have pages or a part of the pages that can only be accessed/visible on the desktop, those pages and/or content will no longer be indexed by Google, and therefore, it won’t show up in the search results.
When more and more people view web content via smartphone, this move came as no surprise. At the same time, there are many websites who have made a conscious decision to not providing certain content for mobile view as people are likely to view and use those content only from the desktop. It’s the fact that some content are just not good for use on mobile screen.
Now that those content will be ignored by Google after March 2021, the website owners must make them at least reachable and viewable by a phone before March. They can worry about the mobile friendliness of those content later, but at least need to make them accessible via phone.