The krita thumbnailer normally used, found online or documented doesn't make previews for file names with a space
Ex: test file.kra(won't have a preview) testfile.kra(will have a preview)
Solution Update the thumbnailer and clear cahed failed thumbnails:
Why this solution, I believe the %i and %o variables aren't being passed properly when they have spaces
I tried it without them, cleared the thumbnails .cache and it doesn't work without the quotes around those
Verify that the sudo touch and tee are aimed at the correct location
# Creates and puts text in the Krita Thumbnailer
sudo touch /usr/share/thumbnailers/kra.thumbnailer
echo $'[Thumbnailer Entry]
TryExec=unzip
Exec=sh -c \'unzip -p "%i" preview.png > "%o"\'
MimeType=application/x-krita;' | sudo tee /usr/share/thumbnailers/kra.thumbnailer
Clear Thumbnailer cache Clear the cache for the bad thumbnails
Verify the path or do it manually
# the directory need to be emptied to ensure that new valid thumbnails are generated
#rm -rf $HOME/.cache/thumbnails/*
#SEO krita files missing thumbnailer/preview krita files with space missing thumbnailer/preview