Everytime I see these things, I always remember why I wrote this. The one that designs and sells Motherboards shouldn't be the one to give long term Firmware support, since they only profit from selling you new Motherboards, thus not wanting to support new things is a good justification to sell you a new Motherboard (Assuming that you want to buy from them again if you feel that they let you down).I contacted Supermicro asking about Milan support for my H11SSL.
Here is their reply (from Apr :12 2021)
After checking with PM, unfortunately, we don't have plan to update the BIOS of the H11SSL to support Milan.
Sorry for the inconvenience!
Clearly not the answer I was hoping for. So I can update my Rome 16 core one day, but it will have to be a higher core Rome. I was hoping to update to a Milan processor.