According to GM there are but 2 licensed 0w40 dexos2 oils. One of those is Castrol &, the other, Mobile-1.
https://www.gmdexos.com/brands/dexos2/index.html
That is not to say there aren’t others that meet the specification requirements, but only 2 that pay royalties to GM to carry the Dexos2 labeling.