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-archive/debian/pool/main/u/unzip/
- 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?
Thanks for reporting. It is a regression as it worked fine a couple of months ago. I didn't notice the change until now. Opened a ticket to track the issue: https://github.com/koreader/koreader/issues/5963
Great news, if it can be corrected.

Do you think that the Home button could have the same behaviour as in the bq firmware: the double press that puts the reader in standby mode is really useful, and the long press that puts the light on is nice too ?
This would be great but I don't know if koreader allows this and if it is reasonable or not to implement it.
@brno Should be fixed in today's nightly.
Thanks! What I call a quick response!
Nope, key events are mapped to a single action. You can remap each button to the single thing you want following https://github.com/koreader/koreader/wiki/Keymapping.
Solved, thanks!
I just installed it... Solved, thanks !