The error you're encountering is because the Testnet binaries are not currently expected to function as the testnet configurations and documents haven't been published yet. For now, it's recommended to use the devnet binaries and configurations for experimenting with Walrus.

You may need to ensure that the staking_object and other necessary configurations are correctly set up in your client_config.yaml file. The configurations for accessing Testnet and Mainnet require certain Sui object IDs to be specified, including system_object, staking_object, and subsidies_object. If you haven't already done so, download the latest configuration file for the Walrus setup directly using: curl https://docs.wal.app/setup/client_config.yaml -o ~/.config/walrus/client_config.yaml. This will help in ensuring you have the most up-to-date configuration necessary for running nodes.