No documented way to set the MAC for a bridge or bond

For networkd, All virtual net devices support general parameters, including MACAddress
and this works as expected if netplan passes through macaddress parameters to netdevs it creates.

root@z1:/etc/systemd/network# cat br0.net*
[NetDev]
Name=br0
MACAddress=00:11:22:33:44:55
Kind=bridge
[Match]
Name=br0

[Network]
Address=192.168.2.1/24

root@z1:/etc/systemd/network# networkctl
IDX LINK TYPE OPERATIONAL SETUP
  1 lo loopback carrier unmanaged
  2 br0 ether no-carrier configuring
 16 eth0 ether routable unmanaged

3 links listed.
root@z1:/etc/systemd/network# ifconfig br0
br0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
        inet 192.168.2.1 netmask 255.255.255.0 broadcast 192.168.2.255
        ether 00:11:22:33:44:55 txqueuelen 1000 (Ethernet)
        RX packets 0 bytes 0 (0.0 B)
        RX errors 0 dropped 0 overruns 0 frame 0
        TX packets 0 bytes 0 (0.0 B)
        TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

root@z1:/etc/systemd/network# cat *bond*
[NetDev]
Name=bond0
MACAddress=aa:bb:cc:00:11:22
Kind=bond
Mode=balance-rr
[Match]
Name=bond0

[Network]
Address=10.2.71.1/24
root@z1:/etc/systemd/network# ifconfig bond0
bond0: flags=5123<UP,BROADCAST,MASTER,MULTICAST> mtu 1500
        inet 10.2.71.1 netmask 255.255.255.0 broadcast 10.2.71.255
        ether aa:bb:cc:00:11:22 txqueuelen 1000 (Ethernet)
        RX packets 0 bytes 0 (0.0 B)
        RX errors 0 dropped 0 overruns 0 frame 0
        TX packets 0 bytes 0 (0.0 B)
        TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

Right, this appears well supported by networkd, but not at all by NetworkManager. I'll file a bug upstream about this.

Adding MAAS; we need to ensure MAAS is generating the expected Netplan once this has been defined.

This is complicated, it appears as though networkd and NetworkManager don't always get the MAC change even if we force re-applying the .link file via udevadm. This will need more work.

Curious what you mean by 're-applying'. Are you syaing it generates the correct configuration the first time, but it cannot subsequently be updated?

The configuration is correctly generated, but requires a reboot. Simply trying to apply the new cloned MAC even with net_setup_link does not appear to work.

I'm marking this a duplicate of bug 1690388: it already contains the cloud-init bits and milestones for SRU; and a bit more information about the issue at hand.