Today after a BIOS upgrade, I almost thought I had locked myself out of my computer. Neither Windows nor Kubuntu would boot, and I was running out of ideas.
After many dead ends, and a couple of frustrating and scary hours, an eventual good web search told me that the upgrade had probably reset my BIOS setup, including the SATA mode.
After setting it back to AHCI, everything went back to normal.
Generalistic and moderated instance.