Mosquitto broker on android 9 hotspot = random broker address

after some years of great and reliable service, my old Android 7 phone, used as hotspot and mosquitto broker, has decided to retire himself. In my previous setup, Mosquitto runs in a termux shell on boot, and with an app/tasker plugin -mqtt client-, I can intercept messages sent from an esp32cam client (I use it as a PIR alarm), then send me sms through tasker and a mail with the captured image through wifi. On android 7 the hotspot address is always 192.168.43.1 and for months I had no problems. Now I have a new phone as hotspot, with Android 9, but I can't replicate my setup: the gateway address, so the mosquitto broker address, changes randomly at every new connection, and I can't fix it on the esp32 and on the mqtt client app.