Not long ago there was some buzz around how WebKit handles 100vh in CSS, essentially ignoring the bottom edge of the browser viewport.
(the short of it: WebKit says this is “intentional” 🧐).

This is the hack to get WebKit to work correclty with a basic flexbox layout.

REFERENCE:
https://allthingssmitty.com/2020/05/11/css-fix-for-100vh-in-mobile-webkit/