Discourse now (as of Nov 2023) has support for passkeys (WebAuthn). It does not appear that the Swift Forum yet supports it.
I would like to request that it does, and hopefully also provide a way to change my login method from whatever it is now (username/password) to passkey.
Thank you! I was also able to set up a passkey and log in using it from another device, all without issue.
I believe this is currently not supported by Discourse. It was brought up in the thread you linked to, but it's listed as a "possible future improvement".