In answer to the customer, Samsung representative at South Korea has mentioned that the company will not dispatch the latest One UI 2.1 for Galaxy S9/S9+ & Note 9. The same answer came from another customer care support when he/she said these flagship phones would not upgrade to the One UI 2.1 version. This time, the person on the other side has given a proper answer that the Galaxy S9, Galaxy S9+ & Galaxy Note 9 users will not test a new update.
The representative says he has confirmed it with the relevant department & there is no schedule for firmware release in the near future. Here is the response from the Samsung customer representative in South Korea.
Your Galaxy S9 & Note 9 models have been contacted by One UI 2.1 update schedule. You may be frustrated and wondering, but we apologize for any inconvenience caused by the product use process. Unfortunately, when confirmed with the relevant department, it is confirmed that there is no support plan for the one UI 2.1 update schedule for the S9 & Note9 models at this time. However, there are a lot of liquid matters such as development and verification related to the update, so there may be internal changes.
The Galaxy S10 & Note 10 series smartphone users are now using One UI 2.1 update. The firmware brings some exclusive features of Galaxy S20 to these older flagship devices of 2018. Unfortunately, it looks like Galaxy S9/S9+ & Note 9 users would not get it. These devices are still running on the Android 10 based One UI 2.0 update.