Yes, you can import nebo files from Kobo Sage or Elipsa
Connect Kobo and copy any files with <anything>.nebo to PC
eject
Connect iOS or Android tablet.
Copy files to a new folder on the SD card
In Nebo: make a suitable Collection and import Notebooks.
It's likely that I can do it direct with a suitable OTG adaptor and the Android File manager.
The actual Nebo files used in the application are not exposed on MTP.