In Discover, scrolling via touch is currently broken. Sliding horizontally between pages works with touch, but neither the list of applications nor the sidebar nor the details page scroll via touch. I reproduced it under both X11 and Wayland, under Manjaro and neon. In other Kirigami apps, scrolling works just fine, it's only broken in Discover.
I also reproduced it both in 5.10.5 and Git.
*** This bug has been marked as a duplicate of bug 380511 ***
Un-duping and using this as the master bug for touch support in Kirigami scrollviews.
Fixed as of Frameworks 5.42 and Discover 5.12.