Downloading all tiles in a bounding box

[Helium314]

I have a style in a JSON file, and want to download all tiles in some bounding box up to the maxzoom as set in the JSON file.
The area is rather small (not more than a few km²), and there is no need to keep the tiles permanently, i.e. caching like it happens when the map downloads a tile after panning is enough (and preferred for simplicity).

The OfflineManager seems overly complicated for essentially prefetching tiles, and can't be used anyway because the style doesn't have a style url (see #609).

Is there a way of getting the mapLibre to download an area that is not currently in view?
Or alternatively, is there a way of providing tiles to put in the offline database (downloading the tiles some other way and giving them to mapLibre)?