I thought it would be worth to share the news that the latest operator release (1.27) now supports the three_data_hall redundancy mode: https://github.com/FoundationDB/fdb-kubernetes-operator/blob/main/docs/manual/fault_domains.md#three-data-hall-replication. The setup is similar to running a FDB cluster across multiple namespaces or multiple Kubernetes clusters. One word of caution, this is a new feature, so you want to make sure you test this setup first for your use case.
If you observe any issues, feel free to open an issue in the GitHub repository.