eventing: Unable to get a basic broker working

Expected Behavior

When I create a broker and look at it with kn broker list, I would expect it to look something like this:

NAME             URL                                                                               AGE    CONDITIONS   READY   REASON
example-broker   http://broker-ingress.knative-eventing.svc.cluster.local/default/example-broker   2d1h   5 OK / 5     True  

Actual Behavior

Instead, it looks like this:

NAME             URL   AGE   CONDITIONS   READY       REASON
default-broker         23h   0 OK / 0     <unknown>   <unknown>

Steps to Reproduce the Problem

1. Install knative-serving and knative-eventing into a kubernetes cluster (I downloaded the serving and eventing yamls from https://knative.dev/docs/admin/install/serving/install-serving-with-yaml and https://knative.dev/docs/admin/install/eventing/install-eventing-with-yaml)
2. install an inmemory channel
3. create a broker kn broker create default-broker
4. list the broker

Additional Info

channel.yaml:

apiVersion: messaging.knative.dev/v1
kind: Channel
metadata:
  name: inmemorychannel

broker describe:

❯ kubectl describe broker default-broker
Name:         default-broker
Namespace:   *** redacted ***
Labels:       <none>
Annotations:  eventing.knative.dev/broker.class: MTChannelBasedBroker
              eventing.knative.dev/creator: developer-admin
              eventing.knative.dev/lastModifier: developer-admin
API Version:  eventing.knative.dev/v1
Kind:         Broker
Metadata:
  Creation Timestamp:  2021-10-27T23:11:59Z
  Generation:          1
  Managed Fields:
    API Version:  eventing.knative.dev/v1
    Fields Type:  FieldsV1
    fieldsV1:
      f:spec:
      f:status:
        .:
        f:address:
    Manager:         kn
    Operation:       Update
    Time:            2021-10-27T23:11:59Z
  Resource Version:  249681561
  UID:               fe68450a-4334-40a5-bacf-03981761dbba
Spec:
  Config:
    API Version:  v1
    Kind:         ConfigMap
    Name:         config-br-default-channel
    Namespace:    knative-eventing
Events:           <none>

Groups thread: https://groups.google.com/g/knative-users/c/k_d6zbD2xZc

Nothing suspicious looking in logs output from imc-dispatcher or imc-controller in the knative-eventing namespace, but I’m happy to attach those logs if that seems useful.