Samsung has already pushed its one UI 3.0 beta based on Android 11 to the Galaxy S20, Note20 and Note10 series but the S10 line seems to be forgotten. Well according to early reports from beta testers, battery life drain is a real problem particularly on the Note10 series which is why Samsung is allegedly postponing the beta for older devices like the S10s.
Post on Samsung Community forum
The beta for the S10 series was reportedly close to being launched but Samsung decided to cancel the premature release and try to work out the underlying issues. In addition, the beta is reportedly postponed for the Galaxy Z Flip and Z Fold2 for now.