I'm not sure what happened, I'm pretty sure I wasn't having issues importing these file types a few weeks ago. Just to be sure I checked the webpage for Reality Converter and yup, GLTF is listed...
Simply drag-and-drop common 3D file formats, such as .obj, .gltf and .usd
I haven't updated anything on my computer, so I dunno how anything could have changed. Anyone know what the deal could be?