I completed the shark but couldn't upload it as Sketchfab wouldn't accept the file format. Maybe it doesn't support Blender 4 or later.
Yeah, it seems to be a bug in Sketchfab. The workaround people have found is to export the model in a 3(x) Blender version, say Blender 3.2 seems to work great for people. Or also formats like FBX or OBJ also people report to bypass the known bug.
