I am attempting to configure a new S/4HANA Cloud and Business Technology Platform for side-by-side extension development using Extending SAP Solutions Using Automated Configurations | SAP Help Portal as a guide.
I'm using this GitHub project to test my configuration. SAP-samples/cloud-extension-s4hana-cloud-business-process: This sample showcases how to complement an existing business process in SAP S/4HANA Cloud with additional business process steps. This involves adding major logic and/or additional data. (github.com)
The process seems to have gone OK, but when I test it, no events arrive at the application.
I found a troubleshooting guide here: Enterprise Event Enablement: Troubleshooting | SAP Blogs which I used to guide this post.
Apologies for all the screenshots, I hope someone will see a problem in one of them. There are questions in BOLD.
The first step in the troubleshooting guide is a connectivity check in S/4HANA, which is successful:

A wildcard Business Partner events (sap/s4/beh/businesspartner/v1/BusinessPartner/*) was added to the outbound topics in a channel named SAP_CP_XF_UDC1. These are bound to the udc1 Event Mesh client.

In the udc1 client in Event Mesh, I can see two events defined. I'm not sure exactly how these events got here, but the look OK to me. Question: Does it matter that only a subset of outbound topics defined in the S/4HANA channel events are listed here?

In the troubleshooting guide, it says "Note: The Topic Space needs to match the namespace that was defined in the Enterprise Messaging service instance."
In my system, the namespace is sap\HANAOD\udc1

In S/4HANA Cloud, I found Topic space in the Communication Arrangement (Not in the Channel). Question: Am I right that the topic space is in Communication Arrangement, not the Channel? If so, my configuration looks right: sap/S4HANAOD/udc1

Next, I check to make sure the second EM client (ems-sap-gis) is able to subscribe to topics in the S/4HANA client (udc1). Here is the JSON from the ems-sap-gis client:
{
"options": {
"management": true,
"messagingrest": true,
"messaging": true
},
"namespace": "udc/sapgis/ems-s4hc",
"rules": {
"topicRules": {
"publishFilter": [
"${namespace}/*"
],
"subscribeFilter": [
"${namespace}/*",
"sap/S4HANAOD/udc1/*"
]
},
"queueRules": {
"publishFilter": [
"${namespace}/*"
],
"subscribeFilter": [
"${namespace}/*"
]
}
},
"version": "1.1.0",
"emname": "ems-sap-gis"
}<br>
I created a queue and added topics for the two events defined in the S/4HANA client (udc1). I also pushed the geo app, which also created a queue that subscribes to the same topics.

To test, I went back to S/4HANA and changed a Business Partner. I checked the "Business Event Queue" app and confirmed that a new event is in the queue. I'm not sure, but I think the fact that I see multiple events in "Business Event Queue" means that things are stuck in S/4HANA.
Alas, there's nothing in the queue in Event Mesh.

Tobias Griebe : S/4HANA events are not making it to Event Mesh and I'm sure it's because I've made a configuration mistake. I'd appreciate it if you could you look this over and see if you can find my mistake(s).