with actual version of Ultimate Member (2.0.21), you can do that with this filter :
add_filter("plugins_loaded", function () {
remove_filter('get_comment_author_link', 'um_comment_link_to_profile', 10000, 3 );
}, 50);
with actual version of Ultimate Member (2.0.21), you can do that with this filter :
add_filter("plugins_loaded", function () {
remove_filter('get_comment_author_link', 'um_comment_link_to_profile', 10000, 3 );
}, 50);