This was unexpected, but I think I’m coping well. These are my notes on configuring netplan networking on my Ubuntu 18.04 server.

1. systemctl disable NetworkManager.service NetworkManager-wait-online.service
2. systemctl mask NetworkManager-wait-online.service
3. systemctl daemon-reload
4. apt install bridge-utils -y
5. edit /etc/udev/rules.d/70-net.rules

   SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{dev_id}=="0x0", ATTR{type}=="1", ATTR{address}=="c8:70:00:9f:d7:72", NAME="eth0"
   SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{dev_id}=="0x0", ATTR{type}=="1", ATTR{address}=="00:e2:ed:17:09:60", NAME="eth1"
   SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{dev_id}=="0x0", ATTR{type}=="1", ATTR{address}=="00:e2:ed:17:09:61", NAME="eth2"
   SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{dev_id}=="0x0", ATTR{type}=="1", ATTR{address}=="00:e2:ed:17:09:62", NAME="eth3"
   SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{dev_id}=="0x0", ATTR{type}=="1", ATTR{address}=="00:e2:ed:17:09:63", NAME="eth4"

6. edit /etc/netplan/01-netcfg.yaml

     version: 2
     renderer: networkd
     ethernets:
       eth0:
         dhcp4: no
         dhcp6: no
       eth1:
         dhcp4: no
         dhcp6: no
       eth2:
         dhcp4: no
         dhcp6: no
       eth3:
         dhcp4: no
         dhcp6: no
       eth4:
         dhcp4: no
         dhcp6: no
     bridges:
       br0:
         dhcp4: yes
         dhcp6: no
         interfaces:
            - eth0
         routes:
            -  to: 192.168.100.0/24
               via: 192.168.45.3
               on-link: true
       br1:
         dhcp4: no
         dhcp6: no
         addresses: [10.45.0.1/24]
         interfaces:
            - eth1
       br2:
         dhcp4: no
         dhcp6: no
         addresses: [10.45.1.1/24]
         interfaces:
            - eth2
       br3:
         dhcp4: no
         dhcp6: no
         addresses: [10.45.2.1/24]
         interfaces:
            - eth3
       br4:
         dhcp4: no
         dhcp6: no
         addresses: [10.45.3.1/24]
         interfaces:
            - eth4
   

7. sudo netplan generate
8. sudo netplan apply
9. reboot

Without my eth1-eth4 devices plugged into a switch, rebooting takes forever.