Hook to modify content on a column on the edit.php (list of posts page)?

you can do this customisation by removing the core author column and replace it with a custom one.

$post_type = "kea_activity";

add_filter("manage_{$post_type}_posts_columns", function ($posts_columns) {
    
    $posts_columns["author_custom"] = "Author";
    unset($posts_columns["author"]);
    
    return $posts_columns;
    
});


add_action("manage_{$post_type}_posts_custom_column", function ($column_name, $post_ID) {
    
    if ("author_custom" === $column_name) {
        
        $author = get_the_author();
        
        echo esc_html($author) . " <strong>information</strong>";
        
    }
    
}, 10, 2);