Minecraft authentication server not reachable over IPv6

If I open the Minecraft launcher on a host with IPv4 turned off, only IPv6, then the launcher goes into offline mode. If I try to join a LAN multiplayer session, I am refused with the message "Failed to login: The authentication servers are currently down for maintenance". It is possible to connect and play over IPv6 if IPv4 is also connected, but at the moment IPv6-only cannot authenticate.

Also the launcher cannot download jar files over IPv6 (MCL-2627), and LAN multiplayer sessions do not appear in scan (MC-92923)