Hello, to be honest, I'm not 100% sure if this issue can be solved on CasC side alone. It seems not. I'm filing it here hoping this will be more obvious to the developer(s) of the plugin.

So, I was able to configure the blob store itself, but didn't find a way to make Jenkins' artifactManager use it.

unclassified:   s3blobstoreconfig:     container: "${ARTIFACT_MANAGER_S3_BUCKET_NAME}"
    region: "us-east-1"
    prefix: "twiddling/"

And this worked fine, for the artifactManager part, though, I tried many combinations to no avail for now. I think I'd need some way to cross-reference the s3blobstoreconfig above, but I do not think it is possible and if this is the right path. Likely not.

Does not work:

 artifactManager:    artifactManagerFactories:      - JCloudsArtifactManagerFactory

NOTE: I have a testing image available if anyone needs anything.