Hello guys, I have the exynos version of the s21 ultra 128gb phantom black.
I got mine delivered on Tuesday the 26th and the battery life the first couple of days was atrocious, was regretting getting the s21 ultra, considering my Samsung S10+ felt better on battery life, after 1.5 years of use!
Anyway yesterday and today has been slightly better (I believe (unless it's in my head)), so I'm assuming once the phone does learn your usage patterns that it gets better, hopefully a little more time/days my battery life will be as good as I expected. I will post in the comments in a few days if it does or doesn't so keep following!
Post your battery life and screen on time in the comments as I'd like to compare.