Bug#1111791: Acknowledgement (systemd: network-online.target reached before IPv6 address is ready)

[Nick Rosbrook]

> I tested here by switching from ifupdown to systemd-networkd and the
> system worked perfectly. Do you recommend that I start using
> systemd-networkd on the servers instead of ifupdown?

I believe that is the recommendation these days, yes:
https://www.debian.org/doc/manuals/debian-reference/ch05.en.html#_the_modern_network_configuration_without_gui.

Glad it's working well for you.