Robosats is the most anonymous p2p service i know for now, with lightning network, so you can use it when on-chain is congested & overpriced fees. No-kyc + you can use it with tor with a new account each times if you want.

Peach bitcoin app: on-chain, no-kyc but you keep a user profile with rating and you own your wallet keys

21bitcoin, hodl hodl : i didn't try it yet