Question: Is there a way to hide the publish menu for the whole network?

Theming
1

Is there a way to hide the publish menu for the whole network?

2

Not recommended.

add_action( 'admin_menu', function() { remove_menu_page( 'pb_publish' ); }, 999 );
3

you can hide just on of the sections if you wish… maybe
an example: https://premium.wpmudev.org/project/ultimate-branding/