Upstream bug: https://bugs.mojang.com/browse/MC-92923

Proposed fix by me: https://bugs.mojang.com/browse/MC-92923?focusedId=1298066&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-1298066

Until this is fixed no vanilla clients will discover the IPv6 address of the servers sending these packets.

Non-vanilla clients can easily patch this and make it work.