Comment 0 for bug 1949761

NetworkManager keyfiles allows to specify "scope: link" routes, by leaving the gateway/next_hop field unspecified, e.g.:

route3=2.2.2.2/7
route4=3.3.3.3/6,0.0.0.0,4

route3=4:5:6:7:8:9:0:1/63,::,5

To keep compatibility, netplan needs to be able to accept "scope: link" routes for the NM backend and render the keyfile accordingly.