Adding RSS feed view
The error just means that the feed row style require fields, but the view being created doesn't have fields.
The error is confusing, since I can create a view like that and add a feed. 

There are two ways for not getting that error: The first one is selecting Table as Display format, and Content as Feed row style, in the page to create a new view.


  


In this way, I got the view without errors.


  


The second way is creating a view without telling the Views module to include a feed. It will be created after.

On the page shown to create a view, I don't select Include an RSS feed, and I click on Save and edit.


  


On the next page, I click on +Add and choose Feed on the drop-down list that appears. (I cannot show it on the screenshot, but I can choose between Attachment, Block, Embed, Entity reference, Feed, and Page.)


  


On the next page, on the bottom, you will get the following error.


  Display "Feed" uses a path but the path is undefined.





  


Click on No path is set, and enter the path you want for the feed.


  


This is close to what the Views module gives you, with an exception: The feed is not attached to any page, since it says Attached to: None.

Click on None and select to which pages the feed must be attached.