no IPV6 from wlan0 via dhcp

[Achim Schaefer]

neither during boot nor during a manual
sudo dhclient -6 -v wlan0
the box does get a IPv6 on WLAN0.

ipv4 works perfectly

verbose output:

Internet Systems Consortium DHCP Client 4.4.1
Copyright 2004-2018 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

no link-local IPv6 address for wlan0

If you think you have received this message due to a bug rather
than a configuration issue please read the section on submitting
bugs on either our web page at www.isc.org or in the README file
before submitting a bug. These pages explain the proper
process and the information we find helpful for debugging.

exiting.

ProblemType: Bug
DistroRelease: Ubuntu 21.04
Package: isc-dhcp-client 4.4.1-2.2ubuntu6.2
ProcVersionSignature: Ubuntu 5.11.0-1019.20-raspi 5.11.22
Uname: Linux 5.11.0-1019-raspi aarch64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl icp
ApportVersion: 2.20.11-0ubuntu65.3
Architecture: arm64
CasperMD5CheckResult: unknown
Date: Mon Oct 4 16:31:14 2021
ImageMediaBuild: 20201022
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
SourcePackage: isc-dhcp
UpgradeStatus: Upgraded to hirsute on 2021-07-17 (78 days ago)