Clemens Doubrava, head of unit at the BSI, maintains a private directory of cloud service providers that state they hold a C5 attestation. The list is growing steadily and was last updated at the end of August: List of C5 attestations
For DiGA, our QuickBird Medical DiGA dashboard provides an overview of the most popular hosting providers: Telekom Cloud Services and Hetzner Online host the most DiGA. Of the two, however, only Telekom holds a C5 attestation. Hetzner Online currently relies on the C5 equivalence ordinance of the Federal Ministry of Health, published as a draft at the beginning of the year: the company says it is waiting to see how things develop.