Comment 14 for bug 510587

This bug is still present in 20.04.
It does not matter if I have listen-on-ipv6 set to a specific address or any. Still the described behaviour is seen.

As a workaround if I set a static IPv6 address on the interface it works. But if the interface is set to auto, or there is a slight delay in setting the address otherwise the problem reappears.

IMHO the solution is that network.target in should not pass until ipv6 auto address mechanism has had a chance to run. This will delay the boot by a second or two. But it will ensure that the interface has an address when daemons start to bind to it.