How to show all articles of subcategories?

Question

Selecting the type of menu item in the "Category Blog, List of All Categories and List of Categories" will result in all links of subcategories not being directed to all articles in the subcategories.

But I want to show directly all the subcategory articles.

main-category sub-categories cat-1 article article ....... cat-2 article article ....... cat-3 article article ....... 

Now, how to show all the articles in the main category?

Answer 1

In the settings of the menu item: blog layout → Choose Enable subcategories "ALL"

UPDATE

FYI: This behavior can also be set globally for all blog layout menu items.
In the section "Parameters of the article manager" → tab "Form / favorite layouts" → "Include subcategories".

Answer 2

first find the params column in the database table ###_extensions whose row name is com_content .

update the internal value in the JSON string, from "show_subcategory_content":0 to "show_subcategory_content":1 , which means support for the level 1 subcategory.
This is a global configuration.

If you want one menu item to support this, find the item in the ###_menu table and add "show_subcategory_content":1 to the params that works.