@OP is asking a way to achieve 100% privacy when convert Bitcoin to Cash, but most people answer it through DEX and P2P platform. Well those exchanges are only protect you to submit KYC, but you're still leave a trace because you give your bank account or e-wallet etc. it doesn't make you achieve 100% privacy, DEX and P2P platform only help you to maintain your privacy, not hide it from the government and chainalysis.

This is tricky and illegal because you're trying to broke the laws on your country, I think except direct P2P and spent your Bitcoin to bought a stuff without submitting KYC, then sell the stuff for cash, there's not many good way.