If you have control of the domain, you can also get an X.509 certificate from any CA (e.g. for free from LetsEncrypt). Then you can put up a new server on that domain with a valid cert. If that server supports ActivityPub, it can provide new public keys for private keys you control for all users on the server, and can use the corresponding private keys to sign messages from any user on that server to any community those users are still subscribed to. In addition, any users on other servers still posting to / interacting with communities on that server would cause their server to send that to the inbox on the new server.

This means any usernames or communities on queer.af should no longer be trusted.