There is an official list of what devices with which Android version is supported
https://developers.google.com/ar/discover/supported-devices
It mention on the top it requires Android 7.
Also some of the devices is running Android 7 out of the box and the page does not mentioning that it need to be upgraded to 8.
Wondering if that really the case as I plan to buy a new mobile shortly and would like to pick one of the "cheap" options from the list that support ARCore.
The list seem to being updated often, last time I checked can't remember seeing any Nokia phones, so I would guess they would mention it on the page if from now on only Android 8 or greater is recommended on all devices.