This error occurs when running my project::: NU1202 Package SQLite.Net.Platform.XamarinAndroidN 3.1.1 is not compatible with monoandroid90 (MonoAndroid,Version=v9.0). Package SQLite.Net.Platform.XamarinAndroidN 3.1.1 supports: net (.NETFramework,Version=v0.0)
Firstly, Xamarin.Android 6.1.0 minimum is required.I tried it in my project, this package is not compatible with Android 9.0, so you are facing this while installing for android 9.0.
This package is still functionnal with "Android N" with a modified Android Platform provider, since there is no update from this package at the moment(last updated 2016/12/15). I do not suggest you to use this package.As magicandre1981 said, you could try to use sqlite-net-pcl