Comment # 3 on bug 1201263 from Jason Mader

This is the best I can come up with, but there's got to be a better way,

systemctl edit --force --full eth0-routes.service
```
[Unit]
Description=Add IPv6 static routes
After=network-online.target
Requires=network-online.target

[Service]
Type=oneshot
ExecStart=sleep 10
ExecStart=/sbin/ip -6 route add 2620:10e:6024:f004::/64 via fe80::1 dev eth0
src 2620:10e:6026:d0a6:92b1:1cff:fe69:b05b metric 256
RemainAfterExit=true

[Install]
WantedBy=multi-user.target
```
systemctl enable eth0-routes