Which PHP page is the Default Posts Page

home.php is the file in the WordPress template hierarchy which is used for the posts page. However, after looking at the Twentyseventeen theme code on GitHub, there is no home.php file provided which means the index.php will be used instead.

Within index.php Twentyseventeen then uses get_template_part to seperate reusable sections of code. The most general of these is the components/post/content.php which looks to be the file displaying your example above.

You can add your get_field function call around line 57 of components/post/content.php and it will display your post metadata.