This is based on what I see, today, in ESP32 -> master (latest) -> API Reference -> Peripherals API -> Inter-Integrated Circuit (I2C) -> Functional Overview -> Register Event Callbacks -> I2C master callbacks.

Says: i2c_master_event_callbacks_t::on_recv_done sets a callback function for master ...

In i2c_device_config_t, I enable ACK checking through 'uint32_t disable_ack_check' which says: "Disable ACK check. If this is set false, that means ack check is enabled, the transaction will be stopped and API returns error when nack is detected ."

But for 'esp_err_t i2c_master_transmit(...)' it ...