tsorin, have you tried Cool Reader 3 on Aura One?
It is supposed to support all Kobo models from Kobo Touch up.
It certainly works on Aura HD and on Aura H2O.
Cool Reader 3 has its own built-in file manager so you can use folder/subfolder structure and forget Calibre. Just name your book root folder with a dot, for example: .BOOKS,
then Kobo software will not attempt to index your books and there will be no slow down
https://www.mobileread.com/forums/sho...d.php?t=272733
Cool Reader 3 is included into that package and it is free, even though some games are not.
Dictionaries (in StarDict format) are supported and working on Aura HD/H2O although their usage is not as convenient and flexible as I would like.
To make this post on topic: this Cool Reader version hopefully works on InkPad 2 as well, because it works on InkPad (I have not tested personally).
But I am interested if it works on InkPad 2.
There is another Cool Reader version for InkPad (hopefully for InkPad 2 as well), though:
https://www.mobileread.com/forums/sho...d.php?t=256917