As a data point - at Hotel Indigo Warsaw this weekend just gone, breakfast offered for whole stay as one of the Diamond amenity options at check-in without me having to ask at all. Decent upgrade too. Good experience overall.
Main negative, as so often the case, is no bill received by email despite asking. Was charged the correct rate anyhow.
ETA: To answer @
Keefy-boy 's query below, this was a cash stay. However my guess is the amenity offer at least would have been the same on points.