Hi all - as far as I'm aware the units shown in Survey123 when you are drawing e.g. a GeoTrace feature are set by your device locale/language. I'm in the UK, but my app is using imperial units. I have double checked that my device language is set to UK English in my settings, but can't get Survey123 to show metric units. Currently using a OnePlus 1, but colleagues are having the same issue (though haven't checked the language on their devices isn't US English)
I've had this same issue and reported it to ESRI at the start of 2020. It is logged as enhancement #ENH-000128512 Survey123 app - when setting a device to language: English (UK) display metric units by default instead of imperial units.
I hope they resolve this. The only workaround offered was as follows: "the only way for all devices to show metric measurements is to change the language settings for all devices to Australian English or Canadian English".