@MGlitch
As far as I know it is not possible to disable Bluetooth only from nickel menu. I tried to disable Wi-Fi, as I was expecting to have BT disconnected as a consequence. No success: I discovered that BT connection stays up even with Wi-Fi disabled! Therefore if I disable Wi-Fi and then launch KOReader, BT gets blocked again! The only way to avoid that is to go in the options and explicitly disable BT manually
Also, I think KOReader does not manage Bluetooth (according to NiLuJe if got it right) so no page turner within this ice app.
@NiLuJe
So, do you confirm BT is not usable within KOReader? Not even with audio devices? Any plan to manage it in the future? Wi-Fi SHOULD be tightly coupled with BT, however as I said above, you can disable Wi-Fi and keep using BT. It is really working (within nickel): I'm able to turn pages from within the standard reader. That's why disabling Wi-Fi before launching KOReader is not sufficient. The issue is that KOReader is doing something different than simply disabling Wi-Fi, with translates in blocking Bluetooth. Can you please explain why after that, Bluetooth gets blocked forever and one can't switch it on, unless don't reboot the kobo? And, is there at least a mechanism to disable BT on launching the app?
Thank you all for your kind responses