diff --git a/.github/workflows/preview-apk.yml b/.github/workflows/preview-apk.yml
index ccb478237..e89bf3005 100644
--- a/.github/workflows/preview-apk.yml
+++ b/.github/workflows/preview-apk.yml
@@ -36,7 +36,7 @@ jobs:
       - uses: nttld/setup-ndk@v1
         id: setup-ndk
         with:
-          ndk-version: r21d
+          ndk-version: r23c
 
       - name: Compile core
         env:
diff --git a/Dockerfile b/Dockerfile
index 0cf193ead..0de294634 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -23,18 +23,20 @@ USER $USER
 ENV ANDROID_SDK_ROOT /home/${USER}/android-sdk
 RUN mkdir ${ANDROID_SDK_ROOT}
 WORKDIR $ANDROID_SDK_ROOT
-RUN wget -q https://dl.google.com/android/repository/commandlinetools-linux-6200805_latest.zip && \
-  unzip commandlinetools-linux-6200805_latest.zip && \
-  rm commandlinetools-linux-6200805_latest.zip
+RUN wget -q https://dl.google.com/android/repository/commandlinetools-linux-8512546_latest.zip && \
+  unzip commandlinetools-linux-8512546_latest.zip && \
+  rm commandlinetools-linux-8512546_latest.zip
 
-RUN yes | ${ANDROID_SDK_ROOT}/tools/bin/sdkmanager --sdk_root=${ANDROID_SDK_ROOT} --licenses
+RUN yes | ${ANDROID_SDK_ROOT}/cmdline-tools/bin/sdkmanager --sdk_root=${ANDROID_SDK_ROOT} --licenses
 
-ENV PATH ${PATH}:${ANDROID_SDK_ROOT}/tools/bin
+ENV PATH ${PATH}:${ANDROID_SDK_ROOT}/cmdline-tools/bin
 
 # Install NDK manually. Other SDK parts are installed automatically by gradle.
-RUN sdkmanager --sdk_root=${ANDROID_SDK_ROOT} ndk-bundle
+#
+# NDK version r23c LTS aka 23.2.8568313
+RUN sdkmanager --sdk_root=${ANDROID_SDK_ROOT} 'ndk;23.2.8568313'
 
-ENV ANDROID_NDK_ROOT ${ANDROID_SDK_ROOT}/ndk-bundle
+ENV ANDROID_NDK_ROOT ${ANDROID_SDK_ROOT}/ndk/23.2.8568313
 ENV PATH ${PATH}:${ANDROID_NDK_ROOT}/toolchains/llvm/prebuilt/linux-x86_64/bin/:${ANDROID_NDK_ROOT}
 
 RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain none
diff --git a/docs/f-droid.md b/docs/f-droid.md
index 90144db73..58392f6f6 100644
--- a/docs/f-droid.md
+++ b/docs/f-droid.md
@@ -1,5 +1,9 @@
 # F-Droid - Overview
 
+- <https://f-droid.org/en/packages/com.b44t.messenger/>
+  is the Delta Chat page on F-Droid.org,
+  the F-Droid-app will show similar information.
+
 - <https://gitlab.com/fdroid/fdroiddata/blob/master/metadata/com.b44t.messenger.yml>
   contains the description and all meta data shown for Delta Chat on F-Droid;
   you can also check if F-Droid recognizes a new version here (they show up at the end)
diff --git a/ndk-make.sh b/ndk-make.sh
index d8f63d228..e87e2a2ea 100755
--- a/ndk-make.sh
+++ b/ndk-make.sh
@@ -80,11 +80,21 @@ export CARGO_PROFILE_RELEASE_LTO=on
 RELEASE="release"
 RELEASEFLAG="--release"
 
+# Work around the bug in the build of Rust standard library.
+# It is built against r22b NDK toolchains and still requires -lgcc instead of -lunwind used in newer r23 NDK.
+# See discussion at <https://github.com/rust-lang/rust/pull/85806>
+TMPLIB="$(mktemp -d)"
+if test -z "$(find "$ANDROID_NDK_ROOT" -name libgcc.a -print -quit)"; then
+    # NDK is does not contain libgcc.a, add a linker script to fake it.
+    echo 'INPUT(-lunwind)' >"$TMPLIB/libgcc.a"
+fi
+
 if test -z $1 || test $1 = armeabi-v7a; then
     echo "-- cross compiling to armv7-linux-androideabi (arm) --"
     export CFLAGS=-D__ANDROID_API__=16
     TARGET_CC=armv7a-linux-androideabi16-clang \
-    cargo +`cat rust-toolchain` build $RELEASEFLAG --target armv7-linux-androideabi -p deltachat_ffi
+    TARGET_AR=llvm-ar \
+    cargo +`cat rust-toolchain` rustc $RELEASEFLAG --target armv7-linux-androideabi -p deltachat_ffi -- -L "$TMPLIB"
     cp target/armv7-linux-androideabi/$RELEASE/libdeltachat.a $jnidir/armeabi-v7a
 fi
 
@@ -92,7 +102,8 @@ if test -z $1 || test $1 = arm64-v8a; then
     echo "-- cross compiling to aarch64-linux-android (arm64) --"
     export CFLAGS=-D__ANDROID_API__=21
     TARGET_CC=aarch64-linux-android21-clang \
-    cargo +`cat rust-toolchain` build $RELEASEFLAG --target aarch64-linux-android -p deltachat_ffi
+    TARGET_AR=llvm-ar \
+    cargo +`cat rust-toolchain` rustc $RELEASEFLAG --target aarch64-linux-android -p deltachat_ffi -- -L "$TMPLIB"
     cp target/aarch64-linux-android/$RELEASE/libdeltachat.a $jnidir/arm64-v8a
 fi
 
@@ -100,7 +111,8 @@ if test -z $1 || test $1 = x86; then
     echo "-- cross compiling to i686-linux-android (x86) --"
     export CFLAGS=-D__ANDROID_API__=16
     TARGET_CC=i686-linux-android16-clang \
-    cargo +`cat rust-toolchain` build $RELEASEFLAG --target i686-linux-android -p deltachat_ffi
+    TARGET_AR=llvm-ar \
+    cargo +`cat rust-toolchain` rustc $RELEASEFLAG --target i686-linux-android -p deltachat_ffi -- -L "$TMPLIB"
     cp target/i686-linux-android/$RELEASE/libdeltachat.a $jnidir/x86
 fi
 
@@ -108,10 +120,13 @@ if test -z $1 || test $1 = x86_64; then
     echo "-- cross compiling to x86_64-linux-android (x86_64) --"
     export CFLAGS=-D__ANDROID_API__=21
     TARGET_CC=x86_64-linux-android21-clang \
-    cargo +`cat rust-toolchain` build $RELEASEFLAG --target x86_64-linux-android -p deltachat_ffi
+    TARGET_AR=llvm-ar \
+    cargo +`cat rust-toolchain` rustc $RELEASEFLAG --target x86_64-linux-android -p deltachat_ffi -- -L "$TMPLIB"
     cp target/x86_64-linux-android/$RELEASE/libdeltachat.a $jnidir/x86_64
 fi
 
+rm -fr "$TMPLIB"
+
 echo -- ndk-build --
 
 cd ..
diff --git a/src/org/thoughtcrime/securesms/ConnectivityActivity.java b/src/org/thoughtcrime/securesms/ConnectivityActivity.java
index ac06a1dc7..81207a98f 100644
--- a/src/org/thoughtcrime/securesms/ConnectivityActivity.java
+++ b/src/org/thoughtcrime/securesms/ConnectivityActivity.java
@@ -43,11 +43,4 @@ public class ConnectivityActivity extends WebViewActivity implements DcEventCent
   public void handleEvent(@NonNull DcEvent event) {
     refresh();
   }
-
-  @Override
-  public void onBackPressed() {
-    // If we did not override this function, the back button in the connectivity view would sometimes
-    // not work, probably because webView.canGoBack() in WebViewActivity.onBackPressed() wrongly returns true
-    finish();
-  }
 }
diff --git a/src/org/thoughtcrime/securesms/LocalHelpActivity.java b/src/org/thoughtcrime/securesms/LocalHelpActivity.java
index 6e01f5fea..982e7f736 100644
--- a/src/org/thoughtcrime/securesms/LocalHelpActivity.java
+++ b/src/org/thoughtcrime/securesms/LocalHelpActivity.java
@@ -69,6 +69,15 @@ public class LocalHelpActivity extends WebViewActivity
     return false;
   }
 
+  @Override
+  public void onBackPressed() {
+    if (webView.canGoBack()) {
+      webView.goBack();
+    } else {
+      super.onBackPressed();
+    }
+  }
+
   private boolean assetExists(String fileName) {
     // test using AssetManager.open();
     // AssetManager.list() is unreliable eg. on my Android 7 Moto G
diff --git a/src/org/thoughtcrime/securesms/WebViewActivity.java b/src/org/thoughtcrime/securesms/WebViewActivity.java
index a86c92d87..272b681ea 100644
--- a/src/org/thoughtcrime/securesms/WebViewActivity.java
+++ b/src/org/thoughtcrime/securesms/WebViewActivity.java
@@ -262,14 +262,8 @@ public class WebViewActivity extends PassphraseRequiredActionBarActivity
     return false;
   }
 
-  @Override
-  public void onBackPressed() {
-    if (webView.canGoBack()) {
-      webView.goBack();
-    } else {
-      super.onBackPressed();
-    }
-  }
+  // onBackPressed() can be overwritten by derived classes as needed.
+  // the default behavior (close the activity) is just fine eg. for Webxdc, Connectivity, HTML-mails
 
   public static void openUrlInBrowser(Context context, String url) {
     try {