In the Power BI Report Server, the configuration settings can be found in the file "RSReportServer.config" which is typically located in the following directory:
C:\Program Files\Microsoft SQL Server\MSRSXX.XX\Reporting Services\ReportServer
The settings related to the communication with the local Active Directory can be found in the "<AuthenticationTypes>" section of the RSReportServer.config file. You can replace the "LDAP" value with "LDAPS" in the "<AuthenticationTypes>" section to configure the PBI RS to use LDAPS.
Here is an example of the relevant section of the RSReportServer.config file:
Please note that changing the RSReportServer.config file can affect the behavior of your report server. It is recommended to make a backup of the file before making any changes, and to thoroughly test the changes before deploying them to a production environment.