Catappult (https://catappult.io) is a distribution channel that I'm using to distribute my game in Aptoide and some Android OEM stores. They are partnering with Unity and are integrated in the editor and in UDP.
However, for the validation of IAP they have a public key like Google Play.
Would be great to have an add-on "Catappult" to validate the purchases that go through Catappult.
The validation is exactly like Google Play (SHA1 key public key starting by MIIB....).