Removing the height styling fixes the problem. I think that all of the custom style on that div can be removed.
My guess is that the design is attempting to keep the footer visible at all times but that doesn't work on Safari or Chrome for me so it's broken for that and causing scrollbar breakage.
The "height: 92vh" styling linked below causes a double scrollbar problem that makes the website nearly unusable for keyboard scrolling.
https://github.com/Raku/doc-website/blob/d550c2ecc3ca0962cd13c688ddba33ae35465574/Website/plugins/page-styling/page-styling.raku#L158
Removing the height styling fixes the problem. I think that all of the custom style on that div can be removed.
My guess is that the design is attempting to keep the footer visible at all times but that doesn't work on Safari or Chrome for me so it's broken for that and causing scrollbar breakage.