When using OptiX, there exist examples which show how to load GLTF and other file formats inside the OptiX advanced samples on github.
There is a dedicated example just for GLTF, and other examples using the ASSIMP library to load other formats like OBJ, STL, PLY etc. though only the geometry is imported and materials are assigned differently, via some scene description text file.
These examples aren’t “real-time” rendering per se, but implement progressive full global illumination renderers with different features in increasing complexity.
You’ll find the links in the sticky posts on the OptiX sub-forum here, as well when reading the list of related threads directly below this very thread.
https://forums.developer.nvidia.com/t/optix-advanced-samples-on-github/48410/4