Albert Bertilsson

This plugin gives you an overview of page templates in your site. You get both an overview of all templates and how many pages they have. You also get a detailed view of all the pages using a specific template.
Usage for this can be to identify unused templates and to find pages using specific templates to change them in some way.

Template Usage

Template Usage gives you a simple overview page of all page templates in your site, allowing you to easily find pages using a specific template.

Shawn Hooper

This plugin generates a list of all the custom page templates available in the active WordPress theme, and shows you how many pages use this template. 
It will also show you if the page contains any Gutenberg blocks or not.
You can also click on the count to access the list of pages that use a specific template.

Page Template Usage Info

Shows you which pages are using which templates, and whether or they are built with Gutenberg or not.

Template Usage vs Page Template Usage Info