I discussed with the AE team, please refer to the following update from them.
Based on the ticket information, if customer can get RGB output by gstreamer, it means that they have already enabled the ISP. I am not quite sure what is right to provide from our side. Could you please collect more information from them?
For steps of porting new camera on i.MX8MP using ISP, please refer to AN13713 ISP New Camera Sensor Porting and Integration Guide for i.MX 8M Plus EVK.