In contrast to, say, Konqueror, Firefox did not work well with the touch screen of my ThinkPad T440s. Scrolling a web page with the finger did not work, and zooming with two fingers did not work either.
Disclaimer: This may or may not work on your computer.
With a simple edit, I was able to use the touch screen the same way as on my mobile phone.
First edit the following file (as root) with your favorite text editor, for instance:
Then add the following line at the bottom of the page:
Save and exit (Ctrl+X and then Y with nano).
Lenovo ThinkPad T440S, Intel Core i7-4600U CPU @ 2.10GHz, 8 GB RAM, 256 GB SSD, Debian Bullseye (KDE)
Lenovo ThinkPad X240, Intel Core i5-4300U CPU @ 2.90GHz, 8 GB RAM, 120 GB SSD, Debian Bullseye (KDE)