How to broadcast a linux machine on LAN before wifi or ethernet connection

If I have a mobile app, capable of scanning devices on my LAN, how can I set up my linux machine (to be present as a device on the LAN), lets say a Raspberry Pi, so that the mobile app can help the machine to connect to WiFi. From the machine I can connect to WiFi with nmcli nmcli dev wifi connect password And this gives the machine an IP on the LAN. This is not what I need. I want that when the linux machine is introduced first time in a LAN, without any changes from the machine, I want to connect it to WiFi from my mobile app. An example of this is how Amazon Echo devices connect to Wifi.