I finally made it to work. Here below the step by step procedure to make it work as the documentation is flaky to say the least and/or not up to date with how it works:
1-you need obviously at least to devices to make an automated range test. Contrarily to what the doc says, it does not matter if your device has not an ESP32 chip (suposedly required to save the csv file that will contain the recorded positions). I tried with a RAK 19007/4631 which is not an ESP32 chip and it works just fine.
2-On both devices sender and receiver (not mentioned anywhere in the documentation) you need to enable range testing in the radio configuration menu. In this range testing sub-menu, you will find three parameters : enable/disable toggle, automated messages frequency (in seconds) - that is how often will the sender send sequential predefined fixed messages with “Seq” as prefix + an incremented number as suffix (example : “Seq1”, “Seq2”, etc)
3-On the sender device (you choose which of the two is the one that will send the automated “Seq#” messages, it does not matter which is the sender, which is the receiver. I tried succesfully using one of the two devices which is fixed as the sender. and I used the second device as the receiver which I moved around. The receiver will receive the “Seq #” messages in the meshtastic app / in the default Long-Fast channel), configure a number of seconds > 0 (for example send a Seq " message every 30 seconds). On the sender leave the last “save to file” parameter to off.
4-On the receiver device, also set the range testing parameter to “on”. But leave the frequency parameter at zero (that is what defines that it is the receiver. Any value above zero will make it a sender for every number of seconds configured in this param). Also leave the save to file disabled.
5-On the receiver (the mobile unit in this procedure), go the the radio confguration menu / Position sub-menu and then modify two GPS parameters as follows (to have the GPS location updated frequently during the range test) : “Position broadcast interval” (reduce the default 900 seconds to for example 15 seconds), and second parameter to change “GPS Update interval” (reduce the default 120 seconds to for example 15 seconds)
6-On the receiver, go to your meshtastic app and in the message channel (default is the public Long-Fast channel) and verify that you receive a “Seq#” message every interval of seconds you configured in the range test / “sender message interval” parameter.
7-Once done with your test, disable both range test on the receiver and sender and configure the two “Position” menu parameters to thei rdefault values (900, 120)
8-On the meshtastic app connected to the receiver device, click on the three dots in top right corner and select “Export rangetest.csv” . This will propose you to save the csv file in your smartphone’s download folder
9-Transfer this rangetest.csv file to your computer. Search on google for “google mymap” and follow import instructions from this google mymap to import the waypoints of the receiver device that your range test produced. You have to select the rx long and rx lat as the waypoint GPS coordinates to be displayed on the “my map” map screen (obviously the sender long ans sender lat correspond to the sender device which remains in a fixed position where you’ve set it to begin with).
Hope this helps others as it took me a few hair to gather this information (and understanding that all youtube tutorials of others who did it are not right anymore since the procedure has chnaged with the latest version recently : previously the receiver did not have to enable the range test : everyone on the public channel could receive the Seq# messages. In the latest verion(s), it is an opt-in model where the receivers will not receive the Seq messages if the range test parameters is not enabled. Even if it is a public channel)
