diff --git a/.gitmodules b/.gitmodules
deleted file mode 100644
index e69de29bb2d..00000000000
diff --git a/app/html-cleaner/.gitignore b/app/html-cleaner/.gitignore
deleted file mode 100644
index 42afabfd2ab..00000000000
--- a/app/html-cleaner/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-/build
\ No newline at end of file
diff --git a/build.gradle b/build.gradle
index dc0c193055f..befe8547da3 100644
--- a/build.gradle
+++ b/build.gradle
@@ -4,10 +4,6 @@ import org.jetbrains.kotlin.gradle.dsl.KotlinCompile
 
 buildscript {
     ext {
-        buildConfig = [
-                'robolectricSdk': 31
-        ]
-
         // Judging the impact of newer library versions on the app requires being intimately familiar with the code
         // base. Please don't open pull requests upgrading dependencies if you're a new contributor.
         versions = [
@@ -61,13 +57,12 @@ buildscript {
         ]
 
         javaVersion = JavaVersion.VERSION_1_8
-        kotlinJvmVersion = "1.8"
     }
 
     repositories {
         mavenCentral()
         google()
-        maven { url "https://plugins.gradle.org/m2/" }
+        gradlePluginPortal()
     }
 
     dependencies {
@@ -82,7 +77,7 @@ project.ext {
     testCoverage = project.hasProperty('testCoverage')
 }
 
-subprojects {
+allprojects {
     configurations.all {
         resolutionStrategy.dependencySubstitution {
             substitute module("androidx.core:core") using module("androidx.core:core:${versions.androidxCore}")
@@ -118,8 +113,8 @@ subprojects {
             }
 
             compileOptions {
-                sourceCompatibility JavaVersion.VERSION_1_8
-                targetCompatibility JavaVersion.VERSION_1_8
+                sourceCompatibility javaVersion
+                targetCompatibility javaVersion
             }
 
             lintOptions {
@@ -153,7 +148,7 @@ subprojects {
 
     tasks.withType(KotlinCompile) {
         kotlinOptions {
-            freeCompilerArgs += "-opt-in=kotlin.RequiresOptIn"
+            jvmTarget = javaVersion
         }
     }
 
diff --git a/cli/html-cleaner-cli/build.gradle b/cli/html-cleaner-cli/build.gradle
index b5afc5dabfb..5d06b5f7ec3 100644
--- a/cli/html-cleaner-cli/build.gradle
+++ b/cli/html-cleaner-cli/build.gradle
@@ -10,7 +10,6 @@ application {
 dependencies {
     implementation project(':app:html-cleaner')
 
-    implementation "org.jetbrains.kotlin:kotlin-stdlib"
     implementation "com.github.ajalt.clikt:clikt:3.4.0"
     implementation "com.squareup.okio:okio:${versions.okio}"
 }
diff --git a/gradle.properties b/gradle.properties
index e87eba41ae7..80938321d3c 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -9,6 +9,6 @@ android.useAndroidX=true
 android.enableJetifier=false
 android.nonTransitiveRClass=true
 
-org.gradle.jvmargs=-Xmx1400m
+org.gradle.jvmargs=-Xmx1400m -Dfile.encoding=UTF-8
 org.gradle.parallel=true
 org.gradle.caching=true
diff --git a/mail/common/src/main/AndroidManifest.xml b/mail/common/src/main/AndroidManifest.xml
deleted file mode 100644
index 384e73586dd..00000000000
--- a/mail/common/src/main/AndroidManifest.xml
+++ /dev/null
@@ -1,2 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<manifest package="com.fsck.k9.mail.common" />
diff --git a/mail/protocols/imap/src/main/AndroidManifest.xml b/mail/protocols/imap/src/main/AndroidManifest.xml
deleted file mode 100644
index ac039d2077f..00000000000
--- a/mail/protocols/imap/src/main/AndroidManifest.xml
+++ /dev/null
@@ -1,2 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<manifest package="com.fsck.k9.mail.protocols.imap" />
diff --git a/mail/protocols/pop3/src/main/AndroidManifest.xml b/mail/protocols/pop3/src/main/AndroidManifest.xml
deleted file mode 100644
index c33a07ad097..00000000000
--- a/mail/protocols/pop3/src/main/AndroidManifest.xml
+++ /dev/null
@@ -1,2 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<manifest package="com.fsck.k9.mail.protocols.pop3" />
diff --git a/mail/protocols/smtp/src/main/AndroidManifest.xml b/mail/protocols/smtp/src/main/AndroidManifest.xml
deleted file mode 100644
index 19d490c4ce4..00000000000
--- a/mail/protocols/smtp/src/main/AndroidManifest.xml
+++ /dev/null
@@ -1,2 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<manifest package="com.fsck.k9.mail.protocols.smtp" />
diff --git a/mail/protocols/webdav/src/main/AndroidManifest.xml b/mail/protocols/webdav/src/main/AndroidManifest.xml
deleted file mode 100644
index 4a3f4ae00db..00000000000
--- a/mail/protocols/webdav/src/main/AndroidManifest.xml
+++ /dev/null
@@ -1,2 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<manifest package="com.fsck.k9.mail.protocols.webdav" />
diff --git a/mail/testing/src/main/AndroidManifest.xml b/mail/testing/src/main/AndroidManifest.xml
deleted file mode 100644
index 5de4ddf34bc..00000000000
--- a/mail/testing/src/main/AndroidManifest.xml
+++ /dev/null
@@ -1,2 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<manifest package="com.fsck.k9.mail.testing" />
diff --git a/plugins/openpgp-api-lib/.gitignore b/plugins/openpgp-api-lib/.gitignore
deleted file mode 100644
index a44cc0f0fae..00000000000
--- a/plugins/openpgp-api-lib/.gitignore
+++ /dev/null
@@ -1,33 +0,0 @@
-#Android specific
-bin
-gen
-obj
-lint.xml
-local.properties
-release.properties
-ant.properties
-*.class
-*.apk
-
-#Gradle
-.gradle
-build
-gradle.properties
-
-#Maven
-target
-pom.xml.*
-
-#Eclipse
-.project
-.classpath
-.settings
-.metadata
-
-#IntelliJ IDEA
-.idea
-*.iml
-
-#Lint output
-lint-report.html
-lint-report_files/*
\ No newline at end of file
diff --git a/plugins/openpgp-api-lib/openpgp-api/.gitignore b/plugins/openpgp-api-lib/openpgp-api/.gitignore
deleted file mode 100644
index a44cc0f0fae..00000000000
--- a/plugins/openpgp-api-lib/openpgp-api/.gitignore
+++ /dev/null
@@ -1,33 +0,0 @@
-#Android specific
-bin
-gen
-obj
-lint.xml
-local.properties
-release.properties
-ant.properties
-*.class
-*.apk
-
-#Gradle
-.gradle
-build
-gradle.properties
-
-#Maven
-target
-pom.xml.*
-
-#Eclipse
-.project
-.classpath
-.settings
-.metadata
-
-#IntelliJ IDEA
-.idea
-*.iml
-
-#Lint output
-lint-report.html
-lint-report_files/*
\ No newline at end of file