@willsj40 @Phischy: The One UI 4 Beta is only available on open network variants of the Samsung Galaxy S21, S21+ and S21 Ultra (CSC = BTU). To check your CSC, head to Settings > About Phone > Software Information > Service Provider Software Version. If BTU is not listed here, then you are unfortunately not eligible to join the Beta.
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 5.0,Android 13 .