I know it would be a PITA for the posties however worst case scenario say I'm trying to get a parcel shipped to me and already generated the label on my end but the other party doesn't have access to a working printer; has anyone had any luck just hand writing the tracking number on the box?

They can then slip it into a post box or rural pickup from letterbox. Not ideal but I assume they must have a way to type the number in in case the barcode doesn't read.