I did run Nina firmware successful on an ESP32 with WiFiNina library in attached MKR Zero.
The required pins are SPI pins
in firmware source:
SPISClass(spi_host_device_t hostDevice, int dmaChannel, int mosiPin, int misoPin, int sclkPin, int csPin, int readyPin);
SPISClass SPIS(VSPI_HOST, 1, 12, 23, 18, 5, 33);
readyPin is not really a spi pin. it is a pin to signal from slave to master that the slave has data to send. you can choose a different pin
for some reason the spi pins are mixed from two spi interfaces of the esp32. I used the documented VSPI pins. (I build the firmware from the source)
in library source
static uint8_t SLAVESELECT = 10; // ss
static uint8_t SLAVEREADY = 7; // handshake pin
static uint8_t SLAVERESET = 5; // reset pin
and NINA_GPIO0 is used, but not defined in library (boards have it in variant). you can choose this pin on the 'host' mcu.
SLAVERESET pin of host should be connected to reset of the esp32
gpio0 is used to put the esp32 into flashing mode for firmware update
and it is used as 'heartbeat' signal of the firmware, so it must be wired
RX, TX are wired for firmware update and are used in Bluetooth mode too.
Bluetooth mode is selected with pin 5 of the esp32.
I didn't test firmware update and Bluetooth