After updating from 21.10 to 22.04 I no longer get the kinetic scrolling effect in Firefox that was working fine before. apz.gtk.kinetic_scroll.enabled is still true.
How do I get it back?
This is another bug with the snap version of Firefox shipped with Ubuntu 22.04. The workaround is to replace the snap version of Firefox with the apt version, e.g. from the Mozilla Team PPA.
See How to install Firefox as a traditional deb package (without snap) in Ubuntu 22.04 (jammy) for more details.