Interesting. Apparently browsers (at least Firefox) uses the OS' setting for this. I still have animations enabled in Windows 10 due to how windows are rendered when they are opened, but the content isn't painted yet.

However, there seems to be way to set this manually in Firefox. [1] Go to about:config and add `ui.prefersReducedMotion` set to `1`. Can be verified with https://animate.style

[1] https://stackoverflow.com/a/59709067