Offline Tile Region Download Does Not Work with Custom (Non-Mapbox) Raster/Vector Tile Sources

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Hello,
I am using the Mapbox Maps Flutter SDK and trying to enable offline map support with a custom style.json file. My style references raster and/or vector tile sources hosted on my own servers (not Mapbox). The style loads and displays correctly online, and loadStylePack works as expected. However, when I attempt to download a tile region for offline use with these custom sources, the download progress remains at zero and no tiles are downloaded. No error is thrown, but the offline region is not populated.
Steps to reproduce:
Create a style.json referencing custom raster/vector tile sources (e.g., WMS, XYZ, or self-hosted vector tiles).
Use this style URL with loadStylePack and loadTileRegion in the Flutter SDK.
Observe that the style pack loads, but the tile region download does not progress and no tiles are cached for offline use.
Expected behavior:
I expect the SDK to download and cache tiles from my custom sources for offline use, as the style specification allows non-Mapbox sources.
Actual behavior:
No tiles are downloaded for offline use when using custom (non-Mapbox) sources, even though the style loads and displays online.
Question:
Is offline tile region download with custom (non-Mapbox) tile sources supported in the Flutter SDK? If not, is there a workaround or is this a known limitation?
Thank you!

Start by reproducing the issue with a custom style.json and non-Mapbox raster or vector sources, using loadStylePack followed by loadTileRegion. Check whether the Flutter SDK documents or implements offline downloads for these sources; done means establishing supported behavior and documenting a confirmed limitation or workaround.

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