override onSupportNavigateUp method to mimic system BACK behaviour

src/org/kde/kdeconnect/Plugins/BigscreenPlugin/BigscreenActivity.java

@@ -97,5 +97,11 @@ public class BigscreenActivity extends AppCompatActivity {
             }
         }
     }
+
+    @Override
+    public boolean onSupportNavigateUp() {
+        super.onBackPressed();
+        return true;
+    }
 }
 

src/org/kde/kdeconnect/Plugins/MousePadPlugin/MousePadActivity.java

@@ -365,5 +365,10 @@ public class MousePadActivity extends AppCompatActivity implements GestureDetect
         imm.toggleSoftInputFromWindow(keyListenerView.getWindowToken(), 0, 0);
     }
 
+    @Override
+    public boolean onSupportNavigateUp() {
+        super.onBackPressed();
+        return true;
+    }
 }
 

src/org/kde/kdeconnect/Plugins/MprisPlugin/MprisActivity.java

@@ -141,4 +141,10 @@ public class MprisActivity extends AppCompatActivity {
             }
         }
     }
+
+    @Override
+    public boolean onSupportNavigateUp() {
+        super.onBackPressed();
+        return true;
+    }
 }

src/org/kde/kdeconnect/Plugins/PresenterPlugin/PresenterActivity.java

@@ -185,5 +185,10 @@ public class PresenterActivity extends AppCompatActivity implements SensorEventL
         };
     }
 
+    @Override
+    public boolean onSupportNavigateUp() {
+        super.onBackPressed();
+        return true;
+    }
 }
 

src/org/kde/kdeconnect/Plugins/RunCommandPlugin/RunCommandActivity.java

@@ -146,4 +146,10 @@ public class RunCommandActivity extends AppCompatActivity {
 
         BackgroundService.RunWithPlugin(this, deviceId, RunCommandPlugin.class, plugin -> plugin.removeCommandsUpdatedCallback(commandsChangedCallback));
     }
+
+    @Override
+    public boolean onSupportNavigateUp() {
+        super.onBackPressed();
+        return true;
+    }
 }

src/org/kde/kdeconnect/UserInterface/About/AboutKDEActivity.kt

@@ -45,4 +45,9 @@ class AboutKDEActivity : AppCompatActivity() {
             @Suppress("DEPRECATION") Html.fromHtml(html)
         }
     }
+
+    override fun onSupportNavigateUp(): Boolean {
+        super.onBackPressed()
+        return true
+    }
 }

src/org/kde/kdeconnect/UserInterface/CustomDevicesActivity.java

@@ -223,4 +223,10 @@ public class CustomDevicesActivity extends AppCompatActivity implements CustomDe
             this.position = position;
         }
     }
+
+    @Override
+    public boolean onSupportNavigateUp() {
+        super.onBackPressed();
+        return true;
+    }
 }

src/org/kde/kdeconnect/UserInterface/PluginSettingsActivity.java

@@ -110,6 +110,12 @@ public class PluginSettingsActivity
 
     }
 
+    @Override
+    public boolean onSupportNavigateUp() {
+        super.onBackPressed();
+        return true;
+    }
+
     @Override
     public void onFinish() {
         finish();

src/org/kde/kdeconnect/UserInterface/TrustedNetworksActivity.java

@@ -137,4 +137,10 @@ public class TrustedNetworksActivity extends AppCompatActivity {
         }
     }
 
+    @Override
+    public boolean onSupportNavigateUp() {
+        super.onBackPressed();
+        return true;
+    }
+
 }