Comment 7 for bug 1886231

Nothig strange about it. Read the whats new page. In 4.20 a change was
made to support two finger scrolling with touchpads, which is pixel
based and too fast. So now pixel based scrolling is slowed down. It is
impossible to support both touchpads and wheel mice that report pixel
scroll amounts. Configure your wheel mouse to generate line or page
scroll events instead of pixel scrolls and you will be fine. Or use flow
mode if you really want to scroll by pixels.