Disabling of email digests is only supported for Jive-x Cloud communities and will likely require a support case, as the necessary system properties may not be accessible to you. This is not supported for Jive-n Cloud environments.
If you're using a Jive-x environment and wish to make this change, please submit a support case in your private Jive Community group and a team member will review this for adjustments. However, if this is being reported for your Preview environment and was already addressed in Customers are receiving newsletters from sandbox environment, then you no further actions are required.
I hope this helps. Let me know if you had any other questions.