@Teleki Battery did tend to take a bit of a hit with the Beta on the S21 series , however experiences varied. You may wish to cleat the cache partition as that can help.
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 .
