.NET for Android error XA1036
error XA1036: AndroidManifest.xml //uses-sdk/@android:minSdkVersion '29' does not match the $(SupportedOSPlatformVersion) value '21' in the project file (if there is no $(SupportedOSPlatformVersion) value in the project file, then a default value has been assumed).
Either change the value in the AndroidManifest.xml to match the $(SupportedOSPlatformVersion) value, or remove the value in the AndroidManifest.xml (and add a $(SupportedOSPlatformVersion) value to the project file if it doesn't already exist).
This error indicates that you have a mismatch between the minSdkVersion element set in your AndroidManifest.xml and the $(SupportedOSPlatformVersion) property value in your project file.
Raise the value of //uses-sdk/@android:minSdkVersion
in AndroidManifest.xml
to match the $(SupportedOSPlatformVersion), or remove //uses-sdk/@android:minSdkVersion
from AndroidManifest.xml and set $(SupportedOSPlatformVersion) in your project
file if it is unset.