My best educated guess they are doing the same “conversion” which is already done for A320 and A330 family - removal of seats and using the floor space for cargo to be secured by cargo nets attached to the seat rails. There are many limitations coming with it like accessibility in flight for inspection and firefighting. Also the floor load limits remain the same as pax which is a far cry from real freighter. It can only work for medical masks transportation which are in a high demand right now ex China. Typical ratio we see is 10 cubic meters to 1 ton, no idea how much they will get cubic wise but MZFW hardly would be a problem. It is a reasonably cheap temporary solution which is only feasible during the current rush, however the STC is reasonably cheap and the only mod cost is seats removal. I must admit the upper deck loading of A380 might be a problem - it is all about manual labor and access.