At least it builds for Debug now...

android/app/build.gradle

@@ -1,3 +1,9 @@
+plugins {
+    id "com.android.application"
+    id "kotlin-android"
+    id "dev.flutter.flutter-gradle-plugin"
+}
+
 def localProperties = new Properties()
 def localPropertiesFile = rootProject.file('local.properties')
 if (localPropertiesFile.exists()) {
@@ -21,10 +27,6 @@ if (flutterVersionName == null) {
     flutterVersionName = '1.0'
 }
 
-apply plugin: 'com.android.application'
-apply plugin: 'kotlin-android'
-apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
-
 def keystoreProperties = new Properties()
 def keystorePropertiesFile = rootProject.file('key.properties')
 if (keystorePropertiesFile.exists()) {
@@ -40,20 +42,11 @@ android {
         targetCompatibility JavaVersion.VERSION_1_8
     }
 
-    kotlinOptions {
-        jvmTarget = '1.8'
-    }
-
-    sourceSets {
-        main.java.srcDirs += 'src/main/kotlin'
-    }
-
-
     defaultConfig {
         // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
         applicationId "dk.cachet.carp_study_app"
-        minSdkVersion 31
-        targetSdkVersion 33
+        minSdkVersion 28
+        targetSdkVersion flutter.targetSdkVersion
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
     }
@@ -80,7 +73,3 @@ android {
 flutter {
     source '../..'
 }
-
-dependencies {
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
-}

android/build.gradle

@@ -6,7 +6,6 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:7.4.2'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }

android/gradle.properties

@@ -1,3 +1,6 @@
 org.gradle.jvmargs=-Xmx1536M
 android.useAndroidX=true
-android.enableJetifier=true
+android.enableJetifier=true
+android.defaults.buildfeatures.buildconfig=true
+android.nonTransitiveRClass=false
+android.nonFinalResIds=false

android/gradle/wrapper/gradle-wrapper.properties

@@ -1,7 +1,6 @@
-#Fri Jun 23 08:50:38 CEST 2017
+#Mon Oct 09 14:52:13 CEST 2023
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.6.3-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.5-all.zip
-

android/settings.gradle

@@ -1,11 +1,29 @@
-include ':app'
+pluginManagement {
+    def flutterSdkPath = {
+        def properties = new Properties()
+        file("local.properties").withInputStream { properties.load(it) }
+        def flutterSdkPath = properties.getProperty("flutter.sdk")
+        assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
+        return flutterSdkPath
+    }
+    settings.ext.flutterSdkPath = flutterSdkPath()
 
-def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
-def properties = new Properties()
+    includeBuild("${settings.ext.flutterSdkPath}/packages/flutter_tools/gradle")
 
-assert localPropertiesFile.exists()
-localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
 
-def flutterSdkPath = properties.getProperty("flutter.sdk")
-assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
-apply from: "$flutterSdkPath/packages/flutter_tools/gradle/app_plugin_loader.gradle"
+    plugins {
+        id "dev.flutter.flutter-gradle-plugin" version "1.0.0" apply false
+    }
+}
+
+plugins {
+    id "dev.flutter.flutter-plugin-loader" version "1.0.0"
+    id "com.android.application" version '7.4.2' apply false
+}
+
+include ":app"