One UI 4 beta is currently available for Samsung Galaxy S21, S21 Plus and S21 Ultra. It should also be released for other Galaxy flagships in the future, but there is no word on when it will happen. First, the One UI 4 beta version is planned to be launched in only seven countries/regions, including China, the United Kingdom, the United States, India, Germany, Poland and South Korea. If you are in one of these locations and have a Galaxy S21 phone, you can go to the Samsung membership app to check if registration for One UI 4 beta is open for you.