Maybe someone like Pakistan. I don't see many African nations aside from possibly Egypt or South Africa have any desire or need for nuclear powered submarines. The only reason I mention South Africa is due to Koeberg Nuclear Power Station, so they do have an education and training pipeline and support services in place.
A country like the Philippines would probably buy German or ROK conventional powered submarines. Vietnam dislikes China. The French and Yankees may come and go, but China will always be there. Spngapore, Indonesia, Thailand, and Malaysia don't do much venturing outside of their immediate areas.
There's also the possibility that South Korea or Japan could invest in nuclear powered boats, but they both have enough in house resources that they could do their own designs. I wouldn't be surprised if the companies who have built Japanese submarines don't already have some design word and limited R&D already done but haven't publicly made it known due to Japanese issues with nuclear power.