Object storage (the S3 API stuff) is the most logical answer here, it’s much simpler and thus more reliable than solutions like Gluster, and the abstraction actually matches your use case. Otherwise something like an NFS share from a central fileserver works too.

But I agree with the other comment that you’re trying to do kubernetes on hard mode and most likely with a worse result.

Thunder has experimental support, haven’t tried it yet though (says it costs extra battery)