I assume you are referring to S4 HANA Cloud, public edition.
In S4 HANA Cloud public edition, there are currently no built-in ways to send events to a Solace PubSub+ broker.
You will be able to connect S4 HANA Cloud to an Advanced Event Mesh broker (AEM) (which is based on Solace PubSub+ Cloud) to send notification events as listed on:
Or you can use extended events using the RAP framework starting with the next release (I believe this is scheduled Q1 2024).
In the meantime you may be able to send those events to SAP Event Mesh and forward them to other brokers from there (e.g. using the in-built webhook or by using a Cloud Integration flow).