Upgrading from macOS Mojave 10.14.2 to macOS Catalina 10.15.4
When I get to the point where I select the disk to install the new OS, I can't select Macintosh SSD. It says "This volume is not formatted as APFS". And I'm stuck here. The disk seems normal, everything seems normal. See attached screenshot (in Norwegian).
iMac 21.5", macOS 10.14