As I know, LocalBitcoins requires your ID documents, so it's not anonymous, I hadn't checked all the others. I switched to Crypton exchange after they listed Bitcoin https://twitter.com/UtopiaP2P/status/1480838807935078402?s=20 Because their exchange is no KYC and decentralized. I don't know what else should be done in order to make you even more anonymous online.