Earlier quoted context omitted.
I've put together an example here but it doesn't seem to work in Firefox 151.0.2 (64-bit): https://favs.eu.org/parallax/ Edit: if the body has class="no-sda", it uses a js fallback.
its beautiful! where can I track the compatibility? and how do I know if I'm hitting the fallback?
updated it with info on what you're using and current baselines comp (Chrome/Edge 115+, Safari 26+, and Firefox behind a flag).