You can set mousewheel.default.delta_multiplier_x and y separately in firefox about:config to increase the x sensitivity,
which makes the horizontal gestures easier to activate;
after slight experimenting, the above fix does not increase the gesture sensitivity.
Instead, just fix the touchpad sensitivity within firefox with the aforementioned option instead. However, you will be stuck with the same extreme scroll behavior in anywhere that is not firefox.
although it makes horizontal scrolling near impossible to use if the x and y values are not similar… Perhaps there is another configuration option to adjust the overscroll gesture sensitivity?
rant
quite disappointing that this option has not been added for at least 3 whole years (the reddit thread for this feature dates back to 2021).
Ryan documents in the 2nd reply, where we can see that the devs for the application toolkit and libinput both says that touchpad scroll sensitivity should not be implemented at their level.
Which then leaves the application, the wm/de/compositor, the kernel, and firmware level.
For the application layer, I believe it is definitely not the right place (even though the workaround for firefox listed above resides here) since we can’t reasonably expect every single developer implements this in every single app; and that’s without taking into account apps that are no longer maintained.
For the firmware level, again I believe it is not suitable to be implemented there given the majority of users probably don’t know how to or don’t want to dump, edit, and flash their firmware for the touchpad if it was even possible in the first place. Furthermore, laptop/touchpad manufacturers probably won’t care about this anyway since Windows handles it.
Which then leaves the kernel and the wm/de/compositor. With the argument from Peter(the libinput dev) saying
The second component is a UI issue and must be handled by toolkit, i.e. GTK/Qt/… Any configuration for scroll speed would have to be set there. This is what Windows does too…
That would then rule out the kernel.