It really depends on the brand from what I remember from my student job delivering fridges for Currys. Some of the Beko ones the longer armed drivers could basically carry under an arm/on a hip, most were an easy two person lift (not like bloody range cookers!).
I’d think the two of you should be able to manage without too much bother. Most normal width fridge freezers are an easy two person lift.
I manhandled a below counter freezer into an awkward gap solo a couple of months back with no issues. Had a bit of help getting it out of the box.
I’d potentially unbox it before doing the steps and wear some grippy/rigger/gardening gloves because sometimes the metalwork underneath is quite thin and digs in to soft hands.