We are still struggling with web views and embedded browsers not supporting viewport relative length units correctly.
Firefox on iOS is still changing vh, lvh and svh when the user scrolls and the navigation bar dissappers:
https://github.com/mozilla-mobile/firefox-ios/issues/22607
Incorrect *vh units are causing havoc for end users and authors. If not mitigated, the page layout can change drastically when scrolling in these browsers.
Kudos to @bramus for opening an interop issue on the subject 🙌