So no fastboot, that's bad, have checked whether "deep flash cable" could help? If you have fastboot surely it has to work, did you follow the guides. Disable driver signature in windows and all that. How did you get the tux LOGO, did you flash wrong ROM.My searches are coming up empty and the fastboot restore isn't working. Is there any unbrick method if the device is booting to the tux logo only?
So no fastboot, that's bad, have checked whether "deep flash cable" could help? If you have fastboot surely it has to work, did you follow the guides. Disable driver signature in windows and all that. How did you get the tux LOGO, did you flash wrong ROM.
You are going to have to provide more information of what you did to get to this point. Miui site will have answers for this problem. Were you updating from updater app on phone? Do you TWRP installed ? Have you tried mi flash tool?failed auto update. anything I can do with this screen: https://i.imgur.com/huZyA2f.jpg ?