A moderator of the Samsung Community in South Korea has confirmed that the company is working on the One UI 2.5 update to make it possible to use the Android 10 navigation gestures with third-party launchers. Right now, while One UI 2.0+ offers the new navigation gestures introduced in Android 10, one is limited to using it with only the stock launcher. Users can, however, use Samsung's own gestures with any third-party launcher of their choice but they are not as smooth and intuitive as Google's gesture system.
This limitation was present on the Pixels as well when Google first released the Android 10 update back in August. However, with the December security patch update, the company made the gestures compatible with third-party launchers.
At the moment, it is not known as to when and for which devices Samsung will be rolling out the One UI 2.5 update. Other new features that the skin could introduce are also not yet known. It is likely that Samsung will release the One UI 2.5 update around August when it prepares to launch the Galaxy Note20. This could mean there are quite a few months of waiting ahead for Galaxy S20, S10, and other Galaxy device owners who were looking forward to using third-party launchers with the Android 10 gesture system.