@Mruk perhaps I'm bring a little too optimistic/naive in hoping that all forum softwares could be exporting to a common format (and co-exist happily 😆), but even that comes with its own caveats, namely in that it'd only be able to support the lowest common denominator, so just posts, topics, and categories.

The Redis (or MongoDB) dump file would be the best resource for the data, though, yes...