Sorry for the delay ��� my Kernel was updated to kernel-default-4.12.14-lp151.28.40.1 on the 13th of March. Leap 15.1 IPv6 NFSv4 Client mount to a QNAP NAS with DNS hostname resolution is now OK. Leap 15.1 Laptop mounting to this Leap 15.1 NFS Server with DNS hostname resolution is now OK but, it's NFSv4 with IPv4. Possible explanation is this SLES 15 Release Notes entry: "NFSv4 with IPv6 is only supported for the client side. An NFSv4 server with IPv6 is not supported." <https://www.suse.com/releasenotes/x86_64/SUSE-SLES/15/#TechInfo.Filesystems.Comparison> I suspect that, we can change the status of this Bug Report to resolved. Thanks and best regards.