Turn Off Avatars Everywhere

Stops avatars from being shown in comments, the admin bar and user lists, saving the image requests.

Code

add_filter( 'pre_option_show_avatars', function () {
    return '0';
} );

Same as unticking "Show Avatars" in Settings > Discussion, but locked in code.

Install WPIDE on your WordPress site (it is free) and open Code Snippets.
Use snippet above adds it from the library in one click. Or copy the code into a new snippet with the same code type.
It is added inactive: review the code and settings, then switch it on.