What is the usage of parameter useInternalMapper, is it documented ?
Does this parameter allow to bypass ZSS authorization for ZLUX ?
Component: Brightside, Zowe API ML
The parameter removed the need for the API Mediation Layer to use ZSS when performing client certificate authentication.
It doesn't change anything with respect to ZLUX and ZLUX usage of ZSS.
Explanation can be found in section "Configure Internal API ML Mapper" available here - Enabling single sign on for clients via client certificate configuration | Zowe Docs