SUMMARY
The "Invert scroll direction (Natural Scrolling)" checkbox option applies opposite results to different KDE apps.  With "natural scrolling" enabled some apps such as System Settings scroll up when a finger is drawn up (toward the keyboard) along the side scrolling area of the touchpad.  Others, such as Falkon, scroll down when the same movement is made.  Disabling "natural scrolling" inverts these apps.  This is in a Wayland Session.

Apps where natural scrolling = screen scrolls the direction of the finger movement
-System Settings
-Discover

apps where natural scrolling = screen scrolls the opposite of the finger movement
-Falkon
-Ksysguard
-Info Center
-Konqueror
-Dolphin
-Konsole

STEPS TO REPRODUCE
1. Select option "Scrolling: Touchpad Edges"
2. Select option "Scrolling: Invert scroll direction (Natural Scrolling)
3. Try touchpad scrolling in different apps

OBSERVED RESULT
Apps have different scrolling behavior

EXPECTED RESULT
Apps should have similar behavior

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 5.20.80
(available in About System)
KDE Plasma Version: 5.20.80
KDE Frameworks Version: 5.76.0
Qt Version: 5.15.0

ADDITIONAL INFORMATION
Dell 7450
5.4-0-52-generic