Comment 9 for bug 1879933

The working example seems to set a default route in the legacy way, using the "gateway4" setting:
  gateway4: 10.245.168.1

While the broken example sets a default route (on routing table 1 only) in the new way, using the "routes" setting.
      routes:
      - table: 1
        to: 0.0.0.0/0
        via: 10.245.168.1
      routing-policy:
      - from: 10.245.168.0/21
        priority: 100
        table: 1
      - from: 10.245.168.0/21
        table: 254
        to: 10.245.168.0/21

Netplan seems to apply the configuration it gets correctly. But when the default route is installed to "table 1" instead of the default routing table, the setup is broken. So this is not a Netplan issue IMO, but whatever provides the configuration (gateway4 vs routes) seems to be at fault here. The default route should be provided using the routes setting, but maybe just leaving out the "table: 1" and routing-policy settings could fix this.

Please re-open (on the Netplan task), if you still think this is a Netplan issue.