Even on the Desktop Web Browser (where I was), by default the scrollbars are hidden (macOS). It is not apparent that the content is scrollable but confined in a frame/container. I had to stumble on it when I graze over the Magic Mouse because the cursor is outside of the content (inside the frame/container).
Contents inside a frame is OK but make it apparent, say, have a thin border, with a lightly different backgound and have the scrollbar forced if the content is larger than the defined height of the frame.
It sometimes breaks thing like "space" to scroll, depends where focus ends up.