If you are a Themes, Icons, or Watch Face seller you do not need a DUNS number since those are closed ecosystems already. If you are an Android developer you will need to get a DUNS number and submit that to the Seller Portal for your Business Registration information.
You can request a global D-U-N-S number from this Link
Even if it opens a partner company do a search for DUNS and it will tell you how to request it.
If you have other questions I’ll try to help or you can sign into the Seller Portal and select Help → contact us and they can assist you.
I understand that there may be some instances where an honest developer writing useful Android apps may not be able to get a DUNS number but this is not required by Play Store and they should publish their app through Play Store.
Hope this helps, let me know if you need clarification
Ron
Samsung Developer Relations