- Struggling With Liver Segmentation in 3D Slicer — Need Guidance

You can definitely do that with TotalSegmenator.

https://discourse.slicer.org/t/new-extension-fully-automatic-whole-body-ct-segmentation-in-2-minutes-using-totalsegmentator/26710

Here’s an example I did recently with it:

In terms of datasets, you can look on the Imaging Data Commons and related resources.