Many thanks for the feedback.
(1) Regarding updating KOReader, would it be OK just to delete the folder in adds and just extract the latest build to the adds folder again? Does this affect the functionality of KOReader in any way?
(2) I followed the instructions for the installation of KOReader menu for the Aura One and it works. To be specific - when Nickel re-boots for update should I select 'handle update' and then full installation when the device boots into KOReader menu?
