Web Serial is required. Safari and Firefox do not expose the needed serial flashing API.
FlockView Web Flasher
Flash the official FlockViewScanner v1.0.0 firmware to an ESP32-WROOM-32 development board from a Chromium-based browser using Web Serial.
Install Firmware
Connect the ESP32 over USB, hold BOOT if your board requires it, then choose the serial port and install the firmware.
Use a data-capable USB cable and close PlatformIO Serial Monitor or any other app using the port.
After flashing, open the Mac app and use Hardware Mode to connect at 115200 baud.