Comment 6 for bug 1747455

Verification done on bionic with netplan.io 0.40.1~18.04.2:

I have verified that a route set to scope: link is correctly accepted and adding to the main routing table:

ubuntu@nice-baboon:~$ sudo netplan --debug apply
** (generate:1231): DEBUG: 18:19:53.369: Processing input file /etc/netplan/50-cloud-init.yaml..
** (generate:1231): DEBUG: 18:19:53.369: starting new processing pass
** (generate:1231): DEBUG: 18:19:53.369: ens3: setting default backend to 1
** (generate:1231): DEBUG: 18:19:53.369: Generating output files..
** (generate:1231): DEBUG: 18:19:53.370: NetworkManager: definition ens3 is not for us (backend 1)
DEBUG:netplan generated networkd configuration exists, restarting networkd
DEBUG:no netplan generated NM configuration exists
DEBUG:ens3 not found in {}
DEBUG:Merged config:
network:
  bonds: {}
  bridges: {}
  ethernets:
    ens3:
      addresses:
      - 10.3.21.29/20
      gateway4: 10.3.16.1
      match:
        macaddress: 52:54:00:4d:3e:84
      mtu: 1500
      nameservers:
        addresses:
        - 10.3.21.25
        search:
        - cloud.cyphermox.net
      routes:
      - scope: link
        to: 10.10.10.0/24
      set-name: ens3
  vlans: {}
  wifis: {}

DEBUG:device lo operstate is unknown, not changing
DEBUG:device ens3 operstate is up, not changing
DEBUG:{}
DEBUG:netplan triggering .link rules for lo
DEBUG:netplan triggering .link rules for ens3
ubuntu@nice-baboon:~$ ip route
default via 10.3.16.1 dev ens3 proto static
10.3.16.0/20 dev ens3 proto kernel scope link src 10.3.21.29
10.10.10.0/24 dev ens3 proto static scope link
ubuntu@nice-baboon:~$