FAB needs alot of work all around in my experience with it..
And MegaScans seems to be gone entirely as far as i can tell, a Search for something on Quixel will show different and most often in my experience better results
On very rare occasion i still use Quixel/Fab… Occasionally Art Station
But the change to FAB has moved me on to prefering none of them and Doubling down on learning Blender/Photoshop/SubstancePainter and just making whatever thing i needed myself
IMO they should have updated Quixel and just added another section to it for whatever they Made FAB for, best i can tell to try and compete with ArtStation and not be Unreal only type assets… A simple catagory or filter would have done them just fine such that you could search by format ( Unreal, FBX, etc )
It really should be this way… it’s clearly a possible thing as GoogleDrive does it and many other sites.. It’s essentially string parsing
substr( . )
Right->FileTypeStringif( FileTypeString === “fbx” )
{
Upload as FBX
}
else
{
Not Supported
}
That’s like half the work of it done for them right there 
Overall the whole thing is kinda trash, but they seem to be trying to fix it in some regards at least, I woudn’t have called it release ready yet personally i would have left quixel opperational until FAB has the same features and whatever we tried to add