When using this secret definition
-----------------------------------------------------------------
kind: Secret
apiVersion: v1
metadata:
  name: secret-bp
stringData:
  broker-props-page1.properties: |
    maxDiskUsage=97
included in this ActivemqArtemis CR definition
-----------------------------------------------------------------
apiVersion: broker.amq.io/v1beta1
kind: ActiveMQArtemis
metadata:
  name: ex-aao
spec:
  deploymentPlan:
    image: placeholder
    jolokiaAgentEnabled: false
    journalType: nio
    managementRBACEnabled: true
    messageMigration: false
    persistenceEnabled: false
    requireLogin: false
    size: 1
    extraMounts:
      secrets:
        - secret-bp
  env:
    - name: JAVA_ARGS_APPEND
      value: -Dbroker.properties=/amq/extra/secrets/ex-aao-props/broker.properties,/amq/extra/secrets/secret-bp/broker-props-page1.properties

You notice the pod is in CrashLoopBackOff, and there is an exception on the pod:

java.io.FileNotFoundException: /amq/extra/secrets/secret-bp/broker-props-page1.properties (No such file or directory)

But if you correct the file name on the secret, to start with a string different than "broker-", like:
------------------------------------------------------------------------

kind: Secret
apiVersion: v1
metadata:
  name: secret-bp
stringData:
  x-broker-props-page1.properties: |
    maxDiskUsage=97
And you correct the broker's definition accordingly

------------------------------------------------------------------------
apiVersion: broker.amq.io/v1beta1
kind: ActiveMQArtemis...

  env:
  - name: JAVA_ARGS_APPEND
    value: -Dbroker.properties=/amq/extra/secrets/ex-aao-props/broker.properties,/amq/extra/secrets/secret-bp/x-broker-props-page1.properties

then, the pod is recreated and runs as expected

sdds