App builder already supports 1000+ free Google fonts, In some cases, you want to use the custom font you can flow the below steps:
Option 1: Ovewrite files font.
Change all your file fonts same name in this folder (Not required to replace all Both, Regular, Medium enough) and replaces.
Rebuild source code
=> In this way, you can use the font name “Poppins” on the App builder but the App gets your custom fonts.
Option 2: Free custom code.
You can follow the official docs from the Flutter website and free change the code to its work.
We do not support custom code, so ensure you know what you are doing.