This is something that is on my list to fix as soon as possible. There’s some resizing issues on iOS that Safari doesn’t fire events for.
If you are self hosting, you can change the code in __start__.js
Samsung stretch issue: Samsung S9 Internet Browser stretches the screen · Issue #2386 · playcanvas/engine · GitHub
iOS is more problematic: See this thread: Orientation and screen squish
If you want to cover past the notch on iOS, you will need to add the view-fit=cover attribute on the HTML too: "The Notch" and CSS | CSS-Tricks