In https://docs.goauthentik.io/docs/sys-mgmt/certificates#certificate-discovery is written:

Mounted directories
Docker Compose: A certs directory is mapped to /certs within the container
Kubernetes: You can map custom secrets/volumes under /certs

It is not clear, on which container the certs must be mounted (server, worker or both). The /certs directory exists on both ;-)

It sould also be mentioned that the user can trigger the import manually by running the system task "Discover, import and update certificates from the filesystem"