My app crashes on devices running Android version below 9

I am testing my app in Samsung remote lab and discovering that it keep crashing in devices running on Android below 9.

Searching on Google made me only more confused and aware of how vast is my ignorance.

build.cradle:    android {    compileSdkVersion 28    buildToolsVersion "30.0.3"    defaultConfig {        applicationId "com.photobangkok.moneytalk"        minSdkVersion 16        targetSdkVersion 28        versionCode 1        versionName "1.0"        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"    }    buildTypes {        release {            minifyEnabled false            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'        }    }}dependencies {    implementation fileTree(dir: 'libs', include: ['*.jar'])    implementation 'androidx.appcompat:appcompat:1.2.0'    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'    testImplementation 'junit:junit:4.12'    androidTestImplementation 'androidx.test.ext:junit:1.1.2'    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'        implementation 'com.google.android.gms:play-services-ads:20.1.0'}

When I try to lower minSDKversion to 14 I got the below error:

Manifest merger failed : uses-sdk:minSdkVersion 14...

I am showing ads in this app so I need to use adroidx.