New SDK versions, gradle properties, and androidx - this seems to solve the previous problems!

android/build.gradle.kts

@@ -7,7 +7,7 @@ plugins {
 }
 
 android {
-    compileSdkVersion(29)
+    compileSdkVersion(30)
     sourceSets {
         getByName("main").apply {
             manifest.srcFile("AndroidManifest.xml")
@@ -25,7 +25,7 @@ android {
     defaultConfig {
         applicationId = "com.unciv.app"
         minSdkVersion(14)
-        targetSdkVersion(29)
+        targetSdkVersion(30)
         versionCode = BuildConfig.appCodeNumber
         versionName = BuildConfig.appVersion
 
@@ -129,8 +129,8 @@ tasks.register<JavaExec>("run") {
 }
 
 dependencies {
-    implementation("androidx.core:core:1.2.0")
-    implementation("androidx.work:work-runtime-ktx:2.3.2")
+    implementation("androidx.core:core-ktx:1.3.2")
+    implementation("androidx.work:work-runtime-ktx:2.6.0-alpha02")
 }
 
 // sets up the Android Eclipse project, using the old Ant based build.

gradle.properties

@@ -0,0 +1,2 @@
+android.useAndroidX=true
+android.enableJetifier=true