AdGuard DNS on Fly.io

I am using AdGuard DNS server on the Fly.io.

I am using a custom domain for it, and it works fine on my Android, because Android uses the URL as a custom DNS setting.

On my Macbook, I am trying to the IPv6 of my app as a custom DNS server, but it doesn’t works.
I am exposing port 53 on my app.

I don’t kown what more to try, do you have any guess about what I can do?