Android phone usually look for the following address for connectivity :

• http://clients3.google.com/generate_204
• https://www.gstatic.com/generate_204
• http://connectivitycheck.android.com/generate_204 But depending on your device and version if may be a different address. You can try to enable verbose logs on your ESP32 and see exactly what URL is called by your device.

If there is a (real) WiFi in the surrounding, try setting your ESP32 to both Access Point and Station mode (AP+STA). By connecting it to a real Wi-Fi network with internet, your devices will see an active connection when they join your ESP32's network. This should eliminate the "no internet" warning, as the ESP32 bridges the internet to your devices, while the devices are still connected directly to your ESP32.