As promised all the way back in March, we can confirm that Samsung's One UI 2.5 update finally delivers support for full-screen navigation gestures in third party launchers. It's unfortunate that it took Samsung so long — Android 11 is probably just weeks away, and Pixels got this feature last year — but better late than never, and we can confirm it works on OneUI 2.5 via the Note 20 Ultra.
For those out of the loop on Android's general development, when Android 10 launched, it didn't support separating gesture navigation from the built-in launcher on Pixels either. It took Google an extra month to roll out support with the Pixel 4, and other Pixel phones picked it up as part of the December 2019 update — the first so-called "feature drop."
At the time, developers that had dived into the changes told me the update was actually quite drastic, and almost constituted a minor version number change, except Google doesn't do that anymore. As a result, predictions claimed it could be a bit before we saw manufacturer-customized versions updated with the feature (though we should point out that OnePlus had no issue). We were prepared for a wait, but I didn't think it would take Samsung almost nine months to get around to it.
I'm told by those of us on staff that have one, the implementation right now is a little "janky" when it comes to things like animations, but that could be something launcher developers can improve on their end. Either way, future Note20, Note20 Ultra, Z Flip 5G, and Z Fold2 owners don't have to put up with Samsung's godawful stock launcher just to keep gesture navigation. They can feel free to replace it with something (better) that has been updated to support it, like Lawnchair 2, Action Launcher, or the timeless Nova Launcher. Hopefully, OneUI 2.5 rolls out to older Samsung phones before Android 11 lands.