Messages like this that go unanswered publicly for so long send a really unfortunate message to other potential designers/customers.
It seems there are several small RISC-V boards using chips that are approximately C906/RV64GC class device (BL808, CV1800B, K510, Spacemit K1, etc.) that are made for a specific board or two that don't make the leap to real data sheets, eval boards, longevity commitments, prices, SKUs on LCSC, etc. that area needed to actually be used in custom designs.
I imagine your use is not one where you can let Sipeed (M1S module) or Pine64 (OX64) manage Bouffalo and you incur the size and cost of introducing middlemen...
I'm not in the market to buy 50K parts, but I've heard others ask this question and it seems that doc on BL808 has kind of stalled out, so I'm interested in learning the answer.