DEX is the way for those countries banning Bitcoin, take a look of Bisq and hodlhodl. Have you completed KYC on centralized exchange you using it before? you need to use Bitcoin mixer to hide your tainted coins, so you couldn't get traced.
Seems to be a solution; but honestly if I was in China, I probably wouldn't risk it. If the usage of non-custodial platforms gets enough publicity, I wouldn't be surprised if the Chinese government would commit entrapment by pretending to be a bitcoin seller or something.