This is due to a series of unfortunate combinations, and happens since sometimes 2017:
ConfigurableBlobStore has been made to extend MemoryBlobStore, but without really initializing the data structures of its base class. In fact, it really does not need to extend it.
New API has been added in the BlobStore interface to deal with parameters, but evidently subclasses were not checked, ConfigurableBlobStore really needs to override those methods
Solving it by making ConfigurableBlobStore not extend MemoryBlobStore, and adding proper implementation for the missing methods...