its modules for magento 2 sub category listing
Display sub categories on category pages with images Simplify navigation on complex product catalogs Easy to use and setup
Enable Tm/Subcategory Module
to Enable this module you need to follow these steps:
Enable the Module
bin/magento module:enable Tm_Subcategory
Run Upgrade Setup
bin/magento setup:upgrade
Re-Compile (in-case you have compilation enabled)
bin/magento setup:di:compile