Might be worth pointing out that this is thanks to Sketch publishing specs[0] for their format, making it easy to write importers/exporters for. As far as I know Figma has yet to do this, so anything that reads Figma files is likely reverse engineered and prone to breakage when Figma inevitably changes their undocumented format.

If I were searching for a Figma alternative, its file format being documented would be a priority because otherwise, one is subjecting themselves to some degree of lock-in.

[0]: https://developer.sketch.com/file-format/