This is an interesting thread. I am intrigued by niche/edge cases such as running AI locally on device.
Some notes:
Gemini Nano is only inside other apps. As far as I can tell, it is not a function in the Gemini app itself. For instance, the "AI enhance" option works in Google Photos without the Gemini app installed. I just wanted to clarify that "Gemini nano" isn't some special offline-capable mode you can select in the Gemini app. It is merely the background AI functionality for other apps such as Google Photos, Google Messenger, Pixel Screenshots, etc. Again, I don't believe the Google app or Gemini app is required for that.
Pixel Screenshots is an installable app in the Play Store, but it just crashes on launch. I installed Google's app 'Android AICore' but it still crashes.
Nothing has asked to install AICore yet. I did install it. Not sure what it 'does'. I will uninstall it shortly.
I did install Gemini on a Pixel 9 (running GOS). It tells you it requires the Google app, so I installed that. I do not believe it requires the Assistant app; however, I see the documentation says some tasks too complex for Gemini right now may be handled by Assistant. Gemini is able to interface with other Google apps, such as Google Keep, and write a reminder or note to yourself. It is not able to interface with any non-Google apps. It does not run offline at all. If you turn off Network access, it immediately notices.
I am intrigued by limiting its accesses and abilities using the App Ops app.