Howto render without shadows in custom gui built using python binding

When setting lightning to `NO_SHADOWS` than all surfaces are black even when enabling indirect light.
In `visualization/Open3DVisualizer.cpp` also the `FillamentScene.GemoetryShadows` function is called when displaying a `TriangleMesh` without shadows, which is not available through python binding of `o3d.visualization.rendering.Scene` Is there an other trick to get surfaces properly rendered when turning off shadows. With sun enabled and any other shadow settings surfaces are rendered with colors visible but the down is shadows make it hard to interpret the data encoded by surface colors.

System Mint 20., Python 3.8 Open3D 0.13.x

BTW:
I also get in my installation the following warnings from python:

```
[Open3D WARNING] Resource request for path /usr/local/lib/python3.8/dist-packages/open3d//resources/default_ibl.ktx failed:
* Code: 2
* Error: Failed to read spherical harmonics from ktx
[Open3D WARNING] Resource request for path /usr/local/lib/python3.8/dist-packages/open3d//resources/default_ibl.ktx failed:
* Code: 2
* Error: Failed to read spherical harmonics from ktx
[Open3D WARNING] Resource request for path /usr/local/lib/python3.8/dist-packages/open3d//resources/default_ibl.ktx failed:
* Code: 2
* Error: Failed to read spherical harmonics from ktx
[Open3D WARNING] Resource request for path /usr/local/lib/python3.8/dist-packages/open3d//resources/default_ibl.ktx failed:
* Code: 2
* Error: Failed to read spherical harmonics from ktx
[Open3D WARNING] Resource request for path /usr/local/lib/python3.8/dist-packages/open3d//resources/default_ibl.ktx failed:
* Code: 2
* Error: Failed to read spherical harmonics from ktx
[Open3D WARNING] Resource request for path /usr/local/lib/python3.8/dist-packages/open3d//resources/default_ibl.ktx failed:
* Code: 2
* Error: Failed to read spherical harmonics from ktx
[Open3D WARNING] Resource request for path /usr/local/lib/python3.8/dist-packages/open3d//resources/default_ibl.ktx failed:
* Code: 2
* Error: Failed to read spherical harmonics from ktx
[Open3D WARNING] Resource request for path /usr/local/lib/python3.8/dist-packages/open3d//resources/default_ibl.ktx failed:
* Code: 2
* Error: Failed to read spherical harmonics from ktx
```
Could these be related. And how to resolve them as the files and the related skybox files do exist. and are writeable for owner and readable for owner,group,others.

Open3d was installed from pypi wheel globally as superuse so that all users can use.