The article shows how to do it recursively for an individual directory, meaning this command needs to be run for each directory.
What I want is showing the total number of files including in subfolders for multiple directories at once, just like what disk usage analyzers do for size.
Ideally, it should be done for the entire directory tree (i.e. a list of all folders and next to each the number of files including in their subfolders), just like graphical disk usage analyzers like Baobab do.