I'm honestly surprised this still isn't an included feature. It makes working without a mouse a lot more difficult. There doesn't even appear to be an add-on that can provide the functionality
I wholeheartedly want this feature to trickle into Firefox for Windows & Linux, since it is already baked into MacOS devices. It is so convenient for those Windows devices with a touchscreen as well.
I was very surprised to see this feature didn't exist when I switched to Firefox. It makes touchpad navigation so much easier that it is kind of a dealbreaker for me. I have to use a different browser when I am using my touchpad. Only thing I disagree with OP on is that left is back and right is forward. Left swipe should be to go forward one page, right swipe should be to go one page back.
As @Starost mentioned, it should go back when swiping from left to right and forward when swiping from right to left. Although it might be configurable
The support I am talking about is probably present in mac OS only but not in Linux and windows versions of Firefox. The feature for navigating back and forth the page using track-pad swipe in laptop is very useful. You don't have to rely on mouse every time you use your laptop. This feature is present in many chromium based browsers like chrome, edge, etc. but Firefox doesn't have this.
We would like you to know we have had it behind a pref in Beta for a few versions now for testing in Win, and will soon be by default in beta. We've called it "Swipe to Nav" or S2N for short. S2N4Win and S2N4Linux. Stay tuned. Thanks for the feedback!