KVM Bridge on Ubuntu 20.04 on Raspberry Pi 4

I cannot get networking inside a guest VM to work with KVM on a Raspberry Pi 4 8GB running the official Ubuntu 20.04 image. I have my networking configured correctly, as far as I can tell. And I'm really hoping someone will tell me I did something wrong and can point me to better documentation. I've been through netplan's docs, a dozen different tutorials on KVM setup, and have even looked at some QEMU docs related to CPU config, because I found that QEMU isn't nearly as well built out for aarch64 as it is for x86_64.

I installed KVM through the same means as I have found in a dozen tutorials:

$ sudo apt install qemu qemu-kvm libvirt-clients libvirt-daemon-system virtinst bridge-utils
$ sudo systemctl enable libvirtd
$ sudo systemctl start libvirtd

Here is my netplan:

$ cat /etc/netplan/01-netcfg.yaml 
network:
    ethernets:
        eth0:
            dhcp4: false
            dhcp6: false
            optional: true
            nameservers:
                addresses: [1.1.1.1, 1.0.0.1]
    wifis:
        wlan0:
            dhcp4: true
            dhcp6: false
            optional: true
            access-points:
                "censored":
                    password: "censored"
    bridges:
        br0:
            interfaces: [eth0]
            nameservers:
                addresses: [1.1.1.1, 1.0.0.1]
            parameters:
                stp: true
                forward-delay: 4
            dhcp4: true
            dhcp6: false
    version: 2
    renderer: networkd

And then I defined it for the KVM domain:

$ sudo mkdir -p /opt/kvm
$ sudo nano /opt/kvm/host-bridge.xml

<network>
    <name>host-bridge</name>
    <forward mode="bridge"/>
    <bridge name="br0"/>
</network>

$ virsh net-define /opt/kvm/host-bridge.xml
$ virsh net-start host-bridge
$ virsh net-autostart host-bridge

I then checked that it's actually present and configured proper:

$ virsh net-list --all
 Name          State      Autostart   Persistent
--------------------------------------------------
 default       inactive   no          yes
 host-bridge   active     yes         yes

After starting the VM creation, I checked that its vnet0 gets added to the bridge properly:

$ sudo virt-install --name Test-VM --ram=2048 --vcpus=2 --cpu max --hvm --disk path=/opt/vhd/test-vhd,size=16 --cdrom /opt/iso/ubuntu-20.04.1-live-server-arm64.iso --network bridge=br0 --graphics vnc

$ virsh domiflist Test-VM
 Interface   Type     Source   Model    MAC
-----------------------------------------------------------
 vnet0       bridge   br0      virtio   52:54:00:64:58:9e

$ brctl show
bridge name     bridge id               STP enabled     interfaces
br0             8000.dca632b43f5b       yes             eth0
                                                        vnet0
docker0         8000.0242aa58079a       no
docker1         8000.024296884d89       no              veth239b4dd
                                                        veth76e81fc
                                                        vethdffe7c7
                                                        vethef20e5a

However, after all of this, networking inside of my guest doesn't seem to work. It just spins and spins trying to get an IP address, but it never gets one. Is there something I've missed?

I also checked that the VM is actually using the bridged interface, and it seems like it is:

$ virsh edit Test-VM
...
    <interface type='bridge'>
      <mac address='52:54:00:64:58:9e'/>
      <source bridge='br0'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>
...

Here's a screen of the guest just spinning. As you can see, I have full network capabilities through the bridge interface on the host to connect to KVM through VNC. Screenshot