Please try the following JS code:

function wpfcf_make_tags_required(){
   jQuery('form input').prop('required', true);
}
jQuery(document).ready(wpfcf_make_tags_required);
document.addEventListener('wpforo_topic_portable_form', wpfcf_make_tags_required);

The code should be added in the current active theme JS  files.

I see that in the Add Topic form, the ID of the Tags input element keeps changing. So, what JQuery code can make it a required field, please?

I tried this but it did not work.

$.wpf_tags.attr("required", true);

Thanks.