The other day, I wrote a keyboard shortcut that you can use to scroll through macOS applicatis. This key combinati works in Safari, but there is an extra combinati that you can use. Scrolling in Safari uses another set of keys
[ macOS: Use these keys to scroll through keyboard applicatis ]
Scroll through Safari
Fn or Opti + the up / down arrow keys to scroll slowly. But in Safari, when you press the space bar it scrolls down e page at a time. And when you press Shift + Spacebar it will scroll to the top of a page.
[ Avoid Endless Scrolling: How to Quickly Return to the Start of a Page in iOS ]