Hello, A quick update to my previous message: I think I found the cause on my system - I'm stupid.
The DHCPv6 Reply from the FRITZ!Box was visible in tcpdump, but my nftables input chain dropped UDP replies from port 547 to port 546 before systemd-networkd could process them. After adding: ```nft udp sport 547 udp dport 546 accept; ``` before the final reject rule, systemd-networkd immediately processed the delegated prefix and assigned the expected /64 to the downstream interface. So this does not appear to be a systemd-networkd bug after all. Sorry for the false alarm, and thank you for any time spent looking into this. Best regards, Andreas
