Named work, with the thing being waited on in mono.
Skeleton rows only where the shape is already known — a table, a list. Never for a single value.
Under 200 ms show nothing — a flash of skeleton is worse than a pause. Over 2 s the label has to say why: booting the installation, reading packages instead, searching docs.typo3.org. This product answers from three sources; which one is running is the useful part.