Eh, not Apache Spark <--> Spaces. Doesn't work out the box unlike Spark <--> AWS S3.
See other child comment above. Faster to use AWS S3 instead of trying to fix it (IIRC can't set the endpoint url or something, which is required for Spaces). :shrug:
I appreciate I'm making a "No True Scotsman" point, but Spark isn't really "a typical S3 client doing basic object storage stuff". I'm thinking of your standard web app persisting uploads and static files.