Ya just grab the plug in for an sfm model, or a use a blender file and export either in blender as a fbx model, then drag and drop the fbx into unity, and convert the fbx into vrm in unity. As for Raven, it was originally a mmd model. Most vrm models are just mmd models that people converted.
Also you can convert any model no matter the format into a vrm model, you just need to turn any Daz, sfm, blender, pmx, vam model into a fbx model in blender first. A lot of the time og blender and sfm files give me trouble because of how the bones and scripts are set up when you try to export them in blender. Fbx, Daz and Mmd models are so much easier to work with.
And like I said before, happy to convert models of your fav characters into workable vrm models.
