Update: this solution does no longer work on later versions of Fedora that switched to Wayland instead of X.org by default. If you don’t want to switch back to X.org and you’re using the GNOME desktop environment, you can enable scroll wheel emulation as outlined here.
With the change to the libinput subsystem, you can now enable this behavior by creating a file /etc/X11/xorg.conf.d/10-libinput.conf with the following content:
Section "InputClass" Identifier "Marble Mouse" MatchProduct "Logitech USB Trackball" Driver "libinput" Option "ScrollMethod" "button" Option "ScrollButton" "8" EndSection
Magically, this function got enabled as soon as I saved the file, without even having to restart X! I’m impressed.