Google has replaced the Google Assistant app on Android with Gemini by default

Google is now changing Assistant to Gemini by default when you download the Assistant app from the Play Store or update it.

This means:

Downloading or updating the Assistant app now gives you Gemini instead.
You can switch back to Assistant in the Gemini app settings.
This might be Google's first step towards replacing Assistant completely with Gemini.
Some users are unaware of the switch and see two Gemini apps on their phones.

Overall, this may suggest Google is phasing out Assistant and transitioning users to the newer Gemini AI technology.