I was a bit wrong about the approach of the new course I’m doing. The final image is mainly composited in Photoshop (Krita for me). Some vector elements are imported into Photoshop as picture elements. Other vector elements are exported as PNG to be used a bump maps in the 3D app, and some as SVG to be used as a basis to extrude geometry. The 3D app is used both to create complex geo based on the vectors, but also quite simple geo (e.g. spheres). A major use of the 3D app is to create interesting lighting (and materials) to export images for compositing in Photoshop.
The ‘UI’ in the course name is a bit misleading. The aim is to create the kind of scene one finds in sci-fi movies where the characters are interacting with some kind of interface, usually holographic, often 3D, for example a 3D holographic map of a star system or something similar. Future tech.