There are some in ROK want US to give them similar access on Submarine Nuclear tech as what US give to Australia under AUKUS. However I also read some ROK pundits that believe they can go more independently, and only need some nuclear submarine integration design help from US.
India Arihant eventough build independently, however India has years of experience running SSN by leasing from Russia. This no surprise that Arihant incorporate that. In sense India can be said semi-independent in reaching Nuclear Submarine stage. Brazil will have big help from French on the design and integration of Nuclear reactor operation and safety. However the reactor is Brazil build and design.
ROK and Japan all have advance capabilities on designing their own nuclear reactor. Thus if Brazil can churn out their own compact reactor for Submarine, both ROK and Japan can do that. It will take more political will by Japan political establishment and public to go with SSN. However if ROK goes that path, Japan will most likely intensified moving that direction also. Something that CCP will not like it.
Still using their latest SSK as base, I do believe will be suitable move to goes independently. Frenchie using their SSK as base for their first SSN, and both KSS3 and Taigei definitely suitable enough as base. It is just matter of Political will to churn out compact reactor for their own SSN, and definitely within reach of both nation Nuclear Industry.