If you try to scroll using the touch pad on Firefox 69 for Chromebook it won't work. The scroll action will not be registered. Two cursors will appear when trying to scrolling. One of the cursors won't move while the other is moving along your finger movement.
It works fine on Chrome 77.
Firefox on Chromebook is the Android version, so this might be a generic Android issue. We need to check that.
It is also unclear if the scroll wheel works on other pages.
Scrolling with the built-in touchpad on Chromebook works outside of webaccess.
I could not recreate this on the Pixel with the Logitech diNovo Edge keyboard so this seems to be a specific problem for ChromeOS.
However, the problem with two cursors appearing happens on the Pixel as well when using Firefox. Chrome works just fine.