Bitmain claims they don't use it on mainnet https://blog.bitmain.com/en/ https://blog.bitmain.com/en/ >Our ASIC chips, like those of some other manufacturers,

Bitmain claims they don't use it on mainnet https://blog.bitmain.com/en/ https://blog.bitmain.com/en/ >Our ASIC chips, like those of some other manufacturers, have a circuit design that supports ASICBOOST. However, the ASICBOOST method has not been used by us on the mainnet. We have not seen any evidence yet on the main net that anyone has used it in the patented way.