Can I use Flutter without Firebase?

Flutter – Google Sign in UI and Authentication

Yes ! you can . Create project in cloud console. Download the JSON and place it in android->app folder, thats it.16 Ağu 2019

Google Sign-in is a free service . To use Google sign-in you have to use Google’s Firebase authentication service. Pricing for Firebase has three tiers, you can see the pricing at this link https://firebase.google.com/pricing/.