both {$unsubscribe_link} and {wmf_ur,.unsubscribe} could works like https://civicrm.wikimedia.org/civicrm/admin/messageTemplates?reset=1#/edit?id=321&lang=en_US as long as added in template

@AnnWF This is more of a general problem rather than specific to the unsub link, if you add the checksum as a token ({contact.checksum_value} or {contact.checksum}) you get invalidChecksum in the preview.

I'm going to say the invalidChecksum issue is a won't fix, because there are good reasons it is this way. We'll just have to expect to see invalidChecksum in the preview. We can fix the missing email though.