www.kde.org has no IPv6 / AAAA entry, but is available over IPv6. ... see https://ip6.nl/#!kde.org To be reachable from pure IPv6 systems this AAAA record would be necessary...
Git commit cc4874dc369e269be11f464a0470d26fe08626c6 by Ben Cooksley. Committed on 24/04/2017 at 21:05. Pushed by bcooksley into branch 'master'. Our SIXXS address is long gone, so let's not publish it anymore. We forgot to remove it for kde.org when we removed it for www.kde.org when decomissioning our SIXXS tunnel as part of their shutdown. M +0 -1 zones/kde.org.zone https://commits.kde.org/sysadmin/dns/cc4874dc369e269be11f464a0470d26fe08626c6
Sorry, the publication of that IPv6 address for kde.org itself is actually an error, which i've now fixed. Previously IPv6 service for www.kde.org and kde.org was provided by means of SIXXS. Unfortunately they've sunset their service, so we've had to withdraw those entries from service. At this time i'm not sure when the hoster of the current machine for kde.org will provide IPv6 i'm afraid, but it is something we will look to add once it becomes available.