Even if you do not have --system-site-package, I can use TensorRT from conda by following the steps below. However, this method does not allow you to use TensorRT installed with apt directly from a conda environment.

$ conda create -n trt_exec python=3.10
$ conda activate trt_exec
$ pip install nvidia-pyindex
$ pip install nvidia-tensorrt
$ pip install scipy
$ pip install opencv-python