According to XDA, Samsung announced this morning that it is opening a One UI 3.0 developer beta based on Android 11 for the Galaxy S20, Galaxy S20+, and Galaxy S20 Ultra 5G. To be accepted into the developer program, you must apply and ask for partnership permission. Samsung will approve applications on a case-by-case basis. Currently in pre-beta, this is just a fancy way of calling the current iteration of the program a closed beta. To request partnership permission to install the developer beta, go to the One UI Beta Program webpage and scroll to the bottom. You'll find a button that says "Apply for Partnership."
Currently, the pre-beta is available for only U.S. and Korean Galaxy S20 devices. In the states, only unlocked and T-Mobile/Sprint models will be allowed to take part in the program while all models in Korea are supported. Once Samsung moves on to the public beta period, support will become available to Galaxy S20 users in China, Germany, India, Poland, the Republic of Korea, the United Kingdom, and the United States (in alphabetical order). While Sammy hasn't said when it will start the public beta period, there will indeed be one.
Besides the latest build of Android (Android 11), the Android "R" beta program will include Samsung's One UI 3.0 beta. This is the manufacturer's proprietary UI designed to keep all of the interface elements on the bottom third of the display. This prevents users from finger cramps created when they are forced to stretch their digits in an attempt to reach the top of the screen.
The Android 11 beta program for the Galaxy S20 Series is arriving earlier than previous years which is something that Galaxy users are happy about. In the past, Samsung was criticized for just getting around to its beta program for the latest Android build weeks after Google disseminated the final version of the latest Android build. For example, the final version of Android 10 was released on September 3rd, 2019. A month later, Samsung started pushing out the Android 10 beta. It would appear that Samsung is weeks ahead of last year's schedule.