Here is a copy of my down load experience from another post on this forum.
I bought my car in Sept 2019 new. I have never signed in to the I-Pace's software. I do not use the Incontrol app. I have not turned on any of the wifi or Bluetooth accesss' in the car. My home wifi is wpa2 and requires both sides' numbers to access wifi. The neighbors' wifis are all protected wifis. Last night I saw on this forum that there was a new update for the Incontrol system and that there were questions about how the car was getting the update. I went out to my car(which is parked in an uninsulated garage) and flipped the slide button over to allow updates, then asked the car to check for updates. The car search a few seconds and then asked if I want to download the 77 mb file. I said yes and read the disclaimer. The car said it was downloading the file. About 14 minutes later it said the file was downloaded. I got out of the car, leaving the door open, and unplugged it. I reached back in and started the car back up without the brake pedal and selected to install the software. I left the door open to help insure the car would not shut down(it worked). I went back inside and 30 minutes later came back out and the S19B_19.40.4-436082 software was installed. No, you do not require any wifi or signups of any cell lines to download updated software to a 2019 Jaguar I-Pace with 2500 miles on it.