systemd-networkd-wait-online.service
On Debian 12, for some reason, /lib/systemd/systemd-networkd-wait-online --any --ipv6 still blocks when all interfaces have appeared, and it’s the same without --any.
Therefore if you have also encountered this issue and the interface name is constant, add -i <interface> to fix this issue.
# /etc/systemd/system/systemd-networkd-wait-online.service.d/override.conf
[Service]
ExecStart=
ExecStart=/lib/systemd/systemd-networkd-wait-online -i eth0 --ipv6