Etopa is a two-factor-authentication app, which runs as a web server and can be accessed using a web browser or using an Android app. Feel free to suggest feature implementations or report bugs by creating an Issue on GitHub.
You can use the Etopa.de instance or host your own.
F-Droid: Add repository and search for Etopa
Google Play Store: Etopa 2FA
Amazon Appstore: Etopa
Samsung Galaxy Store: Etopa
Clone repo
git clone https://ltheinrich.de/etopa && cd etopa
Configure
./configure
Build
DEBUG_SIGN=y make
API server: target/build/etopa
Android APK: target/build/etopa.apk
Web archive: target/build/etopa.tar.xz
Fix Installed Build Tools revision 31.0.0 is corrupted. Remove and install again using the SDK Manager.
# Install build-tools 30.0.3 additionally, then copy both files:
cp $ANDROID_HOME/build-tools/30.0.3/dx $ANDROID_HOME/build-tools/31.0.0/dx
cp $ANDROID_HOME/build-tools/30.0.3/lib/dx.jar $ANDROID_HOME/build-tools/31.0.0/lib/dx.jar