Insert wp_query after the_content with plugin (filter the_content won’t work)

You should remove your hook before query.

function wpse_288691_add_query_after_content( $content ) {

    $ouptut="";

    remove_filter( 'the_content', 'wpse_288691_add_query_after_content' );

    // Do your *** WP_Query ***  and assign result to $ouptut.
    // Reset query by executing `wp_reset_query`.

    add_filter( 'the_content', 'wpse_288691_add_query_after_content' );

    return $content . $ouptut;
}

add_filter( 'the_content', 'wpse_288691_add_query_after_content' );

Do not echo anything inside the filter, only return values.