Just to add a bit of perspective on "buddha nature." From among the hundreds of Indian Mahāyāna sūtras there are less than ten which deal with the tathāgatagarbha notion and related ideas. And there was only ever one Indian commentary written on the subject, which was translated into Chinese in approx. the 5th century CE (there are two other Chinese commentaries on this subject which claim to have been written in India by Indians, but for a number of reasons, likely weren't). Anyway, after being translated into Chinese, traditional histories say that this Indian commentary disappeared from the Indian Mahāyāna scene for nearly half a millennium until it was rediscovered by Maitrīpāda in the 11th century. In the interval, the vast majority of significant Indian Mahāyāna authors say nothing on the subject until at least the 8th century, and even after that little is said outside of Vajrayāna contexts. Thus, there's every indication that the tathāgatagarbha theory wasn't a pressing concern for most of the major Indian Mahāyāna commentators.
All the best,