Works just fine in WP6

using this plugin for forever, it just laks the feature to fetch external sources,
to accomplish this I added this in plugin.php

if (isset($attrs['url'])) {
    return file_get_contents($attrs['url'], 0, stream_context_create(["http"=>["timeout"=>3]]));
}

this will fetch external URLs with the shortcode [includeme url=]

With WP6 session data is somewhat cached, which caused some issues, but overall it works just as expected.