Although personally the Oppo Find N is my favorite device with a foldable screen. Software in my opinion is still won by Samsung with One UI used on Samsung Galaxy Z Flip and Z Fold.
Samsung Galaxy Z Fold4 and Flip4, are the first two straight out of the box already running One UI 4.1.1 built on Android 12L.
For those who don't know, Android 12L is an Android operating system that has been optimized for friendly use with large screen, foldable and multi-tasking devices. Examples are app docks, gesture control features for quick access, drag & drop, smoother performance and more.
Recently, two devices with Samsung's foldable screen last year, the Galaxy Z Fold3 and Z Flip3, have started receiving this update. This update is around under 500MB and is rolling out in stages starting with users in South Korea. Users of this class device, after the update is installed, you will be able to use some of the features and functions that are available on Z Fold4 and Z Flip4.