After dozens of attempts a few weeks ago, Tim and I were unable to participate in the Samsung One UI 2.0 beta program for Galaxy S10 and Galaxy Note 10+ unlocked devices. After telling us tonight that Samsung may be freeing up slots for unlocked devices, we both joined! The Samsung One UI 2 beta program is available again!
If you want to register in the US, you need to open the Samsung Members app and look for a special box where you can sign up for the One UI 2 Beta link. When you see this field, tap on it and then follow two more screens with blue buttons that allow you to register your device. It should be that easy when you see the "Register" field on the home page. (Tip: if the check box disappears before you can tap it, close the app, open it, and tap as quickly as you can.) If you make a timeline after one or two tries, you should be able to
I'd like to point out that on my Galaxy S10e, I've tapped the last blue registration button, which returned me to the Samsung Members' main page without confirmation that I'm ready am. After opening "Settings"> "System Update", I was able to search for the beta update and download it.
The S10 is a cool 2.1 GB. So make sure you have Wi-Fi ready and enough space available.  Cheers Scott!