No matching function for call to 'BLEStringCharacteristic::read(arduino::String)' [ARDUINO NANO 33 BLE SENSE]

I think you should be using serviceOutput.value()

String BLEStringCharacteristic::value(void)
{
  String str;
  int length = BLECharacteristic::valueLength();
  const uint8_t* val = BLECharacteristic::value();

  str.reserve(length);

  for (int i = 0; i < length; i++) {
    str += (char)val[i];
  }

  return str;
}