As you can see above I'm trying with com.linkedin.domain and domainProperties for the value and the aspects but it doesn't work. Are there any examples of the payloads required to create new entities through the REST.li API? Thx!

You can use java or python emitter library to do this. Examples can be found here. Its easier than creating jsons directly.

thanks for your answer @careful-pilot-86309, actually we managed to create the entities using the python emitter but I'd like now to understand how to do it using the REST.li API

Any special usecase where you need to directly connect to REST.li? Meanwhile you also have below option: https://datahubproject.io/docs/generated/ingestion/sources/openapi/ Not sure if this is what you want but just giving you option.

We're trying to understand the best way to automatically push the metadata of our data products to Data Hub. Apart for the emitters we'd like to see how easy/difficult is to create the entities using the API