I solved my need.
I get the bytes from the EEPROM as well.
#define MY_IP_ADDRESS_B0 EEPROM.read(xxxx)
....
#define MY_IP_ADDRESS_B3 EEPROM.read(yyyy)

Then I define the address of the gateway like this:
#define MY_IP_ADDRESS ((uint32_t)(MY_IP_ADDRESS_B3) << 24) | ((uint32_t)(MY_IP_ADDRESS_B2) << 16) | ((uint32_t)(MY_IP_ADDRESS_B1) << 8) | (uint32_t)(MY_IP_ADDRESS_B0)

This applies to the other addresses required for the operation of an MQTT gateway.
Hopefully this sharing is useful.
Thank you

The 2.2.0-rc.1 version in development seems to solve the problem.
See also the message : https://forum.mysensors.org/topic/6684/serial-gateway-restarting/30
Can you explain the change in the new version?
Thank you.

I tested the solution proposed above.
It works very well.
I can send to the controller the subscription topic of the gateway, its IP address, etc. during the presentation phase of the gateway.
Thanks again.