To sell BTC, you can use a cryptocurrency exchange or a P2P platform like Coinbase, Binance, Kraken, or LocalBitcoins. On an exchange, create a sell order, specify the amount you want to sell, and choose a price. On P2P platforms, you can find buyers and negotiate directly.
Correction: LocalBitcoins is no longer available for exchange. This is no longer available at all.
The platforms you listed are not the best in terms of confidentiality, because these centralized cryptocurrency exchanges in the first place, and not p2p platforms. These acquired these functions much later.
For direct exchange of p2p between bitcoin users, bisq is better suited.
The times of direct p2p bitcoin exchange in cafes are far behind us and no one will do that now. In any case, you will have to use some kind of exchange platform. As a last resort, you can use bestchange aggregator, which offers exchangers (intermediaries and guarantors of security of transactions between users).