On the other hand, saying Signal is insecure because of what happened is like when my neighbor installed a top-quality security door, then left the keys hanging outside and had a visit from burglars. Not to mention, of course, that it's simply not the right tool for this level of confidentiality.
If you have a fediverse account, you can quote this note from your own instance. Search https://mastodon.bsd.cafe/users/stefano/statuses/114234667746044272 on your instance and quote it. (Note that quoting is not supported in Mastodon.)