The community moderator said the work is in the review process. You can check the complete statement below (translated):
“Currently, it is in the review phase for the application of One UI 2.5 to the 9 series. Following the instructions from the management to prepare customers to experience various SW, we are reviewing the functions that can be installed and re-identified the current memory situation.”
Samsung’s One UI 2.5 comes with many new features but they won’t be coming to all devices due to hardware limitations. There’s no official confirmation about the release date of the One UI 2.5 for the Galaxy Note 9 and S9 series but the update is expected to be here for eligible Galaxy devices by end of the next month.