XT not updating over wi-fi and / or Garmin Express

Garmin confirm that the XT should update via either Wifi or Express.
(Althoughm, currently, mine won't! Annoying. Get as far as the estimate time (4+ hours), allows a quick software update and then it hangs before eventually spitting out an error message. WiFi and Express. Unit is new, bought it a few months ago, only just opened the box. Maps appear to date from 2019/20 and there's 13gb or so to update - perhaps I need to add an SD card. Further investigation required...)

You don't need an sd card. We have a XT on one of our blood bikes with ne sd card and the maps update fine, because I did them .

Remember only firmware & maps will update over wifi, 'Cyclops' (speed cameras) have to be done via Express. Personally, I always update everything via Express on a lap top.