Comment 6 for bug 1750392

OK, I have it working for me using my ipv6 test bench (https://github.com/daxtens/ipv6-config-demos)

Systemd-networkd:

root@slaac-rdnss-networkd:~# ip a list temporary
root@slaac-rdnss-networkd:~# sudo nano /etc/netplan/60-ipv6.yaml # add ip6-privacy: true
root@slaac-rdnss-networkd:~# sudo netplan apply
root@slaac-rdnss-networkd:~# ip a list temporary
113: eth0@if114: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 00:16:3e:6c:32:b7 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet6 fd8f:1d7d:b142:0:c9f6:a048:7d3d:d7b0/64 scope global temporary dynamic
       valid_lft 86399sec preferred_lft 14399sec

NetworkManager:

root@slaac-rdnss-network-manager:~# ip a list temporary
root@slaac-rdnss-network-manager:~# nano /etc/netplan/60-ipv6.yaml
root@slaac-rdnss-network-manager:~# sudo netplan apply # add ip6-privacy: true
# wait a couple of secs
root@slaac-rdnss-network-manager:~# ip a list temporary
69: eth0@if70: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 00:16:3e:be:4c:e9 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet6 fd8f:1d7d:b142:0:55c8:3d0f:558d:2f20/64 scope global temporary dynamic
       valid_lft 86392sec preferred_lft 14392sec

The package is in the same ppa at version 0.39+dja2.2, and I'll submit a PR shortly.

Regards,
Daniel