Hi, S21 Ultra unlocked is working 100% with AT&T eSim since the new beta version 3. Just scan the QR, follow the procedure and that's it!
eSim as primary with AT&T service and a secondary SIM with MVNO Hello Mobile (TMobile) service. It works perfect, WiFi calling for AT&T 100%.
I had the same problem. I tried going to eSIM for all three betas. It looked like it worked, but there wouldn't actually be any connection. The previous two betas I had T-Mobile revert me back to the physical SIM card. This time, I decided to do a factory reset, which I did from the Recovery Mode screen. After the reset, the eSIM started working without me doing anything else. I turned off SIM 1 to remove the physical SIM icon from the screen. My service is working good with connection to 5G in my neighborhood.
I just tried on tmobile as well using convert to esim. As warned it disabled my physical sim but the esim didn't work. Just back from store with new simcard