It is important to ensure your IPv6-only docker server is secure.
First configure your firewall to allow secure shell (SSH), port 22, so that you can maintain your remote connection.
Then turn on your firewall with default deny incoming and default deny routing rules.
This ensures your server is secure-by-default, and only then should you allow routing to the specific containers and ports that you want to expose.
My server runs Ubuntu, so these instructions are based on the Uncompliciated Firewall (UFW), but similar considerations apply to other platforms