[G4 Themes and Apps] mvaenskae:
Cheers,

reporting the same issue on latest Xiaomi.eu Beta-7.7.20 and working Magisk 13.3 on a Xiaomi Redmi Note 4 Global Edition.

Logcat reports the following for the application using

adb logcat *:W

07-27 16:48:37.904 9538 9538 W System.err: java.io.FileNotFoundException: /storage/emulated/0/kppd (Permission denied)
07-27 16:48:37.905 9538 9538 W System.err: at java.io.FileOutputStream.open(Native Method)
07-27 16:48:37.905 9538 9538 W System.err: at java.io.FileOutputStream.<init>(FileOutputStream.java:221)
07-27 16:48:37.905 9538 9538 W System.err: at java.io.FileOutputStream.<init>(FileOutputStream.java:108)
07-27 16:48:37.905 9538 9538 W System.err: at com.alaskalinuxuser.kppdcontrol.InstallActivity.installKPPD(InstallActivity.java:84)
07-27 16:48:37.905 9538 9538 W System.err: at java.lang.reflect.Method.invoke(Native Method)
07-27 16:48:37.905 9538 9538 W System.err: at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
07-27 16:48:37.905 9538 9538 W System.err: at android.view.View.performClick(View.java)
07-27 16:48:37.905 9538 9538 W System.err: at android.view.View$PerformClick.run(View.java)
07-27 16:48:37.905 9538 9538 W System.err: at android.os.Handler.handleCallback(Handler.java)
07-27 16:48:37.905 9538 9538 W System.err: at android.os.Handler.dispatchMessage(Handler.java)
07-27 16:48:37.905 9538 9538 W System.err: at android.os.Looper.loop(Looper.java)
07-27 16:48:37.905 9538 9538 W System.err: at android.app.ActivityThread.main(ActivityThread.java)
07-27 16:48:37.905 9538 9538 W System.err: at java.lang.reflect.Method.invoke(Native Method)
07-27 16:48:37.905 9538 9538 W System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)
07-27 16:48:37.905 9538 9538 W System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)

This is the output when not searching for warnings and above:

07-27 16:50:57.920 9538 9538 W System.err: java.io.FileNotFoundException: /storage/emulated/0/kppd (Permission denied)
07-27 16:50:57.920 9538 9538 W System.err: at java.io.FileOutputStream.open(Native Method)
07-27 16:50:57.920 9538 9538 W System.err: at java.io.FileOutputStream.<init>(FileOutputStream.java:221)
07-27 16:50:57.920 9538 9538 W System.err: at java.io.FileOutputStream.<init>(FileOutputStream.java:108)
07-27 16:50:57.920 9538 9538 W System.err: at com.alaskalinuxuser.kppdcontrol.InstallActivity.installKPPD(InstallActivity.java:84)
07-27 16:50:57.920 9538 9538 W System.err: at java.lang.reflect.Method.invoke(Native Method)
07-27 16:50:57.920 9538 9538 W System.err: at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
07-27 16:50:57.921 9538 9538 W System.err: at android.view.View.performClick(View.java)
07-27 16:50:57.921 9538 9538 W System.err: at android.view.View$PerformClick.run(View.java)
07-27 16:50:57.921 9538 9538 W System.err: at android.os.Handler.handleCallback(Handler.java)
07-27 16:50:57.921 9538 9538 W System.err: at android.os.Handler.dispatchMessage(Handler.java)
07-27 16:50:57.921 9538 9538 W System.err: at android.os.Looper.loop(Looper.java)
07-27 16:50:57.921 9538 9538 W System.err: at android.app.ActivityThread.main(ActivityThread.java)
07-27 16:50:57.921 9538 9538 W System.err: at java.lang.reflect.Method.invoke(Native Method)
07-27 16:50:57.921 9538 9538 W System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)
07-27 16:50:57.921 9538 9538 W System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)