I updated to the latest version of Krita and it crashed for an unknown reason. Now, when I try to open the files (unsaved before the crash), I get an error message saying the file types are unknown. How can I fix this? I have a piece in there that I'm rather proud of, and I need to work on it.

I have the same problem

I think I know what causes this... The autosave files, for some reason, are marked internally as krita files. In 3.3.0, I've added code to look into the file to see what the file type is: this helps with files saved with the wrong extension. So, sometimes, you get a PNG file saved with a .jpg extension, or the other way around. For Krita files, this means that sometimes the file is recognized as a zip file instead of a krita file (a Krita file _is_ a zip file, but with some peculiarities). I've fixed that, and it'll be in 3.3.1, and I probably will release that within a week. But for now, either get an older version of Krita to open that file. If that doesn't work, message me personally, and I'll reply and try to check your files and see whether it can be restored.