Thanks, it works!
Some .deb files where apparently corrupted in ko-deps.tar.gz
I had to get other copies on the internet.
If this can be useful for other people, I found them in 2 places:
-
https://cloudfront.debian.net/debian.../main/u/unzip/
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http://ftp.attica.net.nz/kali/pool/main/i/
Just one thing doesn't work as I expected: when I switch to "Black Mode" in koreader, only the colors of the pictures are inverted. The text remains in black color against white screen. Is it a bug or a limitation of the bq reader itself?