SUMMARY External mice confuse touchpad when 'Left Handed Mode' is enabled. If one is plugged in from the start then external mouse works as expected. Right mouse button is the primary. However touchpad is quite the opposite, right mouse button remains the secondary. So it's really hard to use them together. If the machine is started without any external mice, (and left handed mode is still turned on) touchpad works as expected. STEPS TO REPRODUCE 1. Enable 'Left handed mode' in System Settings 2. Connect an external mouse 3. Reboot the system OBSERVED RESULT The primary button of the external mouse is on the right while it's the secondary for the touchpad EXPECTED RESULT All pointer devices' buttons should be swapped SOFTWARE/OS VERSIONS Operating System: Arch Linux KDE Plasma Version: 5.19.4 KDE Frameworks Version: 5.73.0 Qt Version: 5.15.0 Kernel Version: 5.4.58-1-lts OS Type: 64-bit
There's an option to do the same thing in the Touchpad page. If you also want to swap the buttons, you can do it there.
(In reply to Nate Graham from comment #1) > There's an option to do the same thing in the Touchpad page. If you also > want to swap the buttons, you can do it there. Mouse & Touchpad indeed has a Mouse and then a Touchpad page right below it, however, it's completely unusable because it says "No touchpad found", even though there is one, and it works (buttons are still swapped).
Aha, that means you don't have Libinput installed or active, and instead are still using the old unmaintained Synaptics drivers. These drives aren't supported anymore in Plasma 6. If you do want to use them, I'm afraid it's a "you're on your own" situation.