Reading the documentation shows that Before you provision a server for the first time, you should add your SSH keys to your account. You can do this from the your accounts SSH Keys page in the Forge dashboard.
So you need to go to the copy you public key from you computer and the paste into the Forge ssh add key session, once this is added and saved, and you go back to tableplus to use the database link it then becomes a breeze at this point. Documentation can be found here: https://forge.laravel.com/docs/accounts/ssh.html[enter image description here]1