Whats your CSC you find it in Settings - About Phone - Software Information - Service Provider software information if the country code is incorrect it won't give you automatic software updates OTA
The csc; Settings -> About Phone -> Software Information -> Service Provider Software Version(look for the most repeated group of 3 letters); thats your csc
You probably have a carrier locked phone, and that carrier hasn't released an update.
I bought a S10 5G off Fleabay that was advertised as being new. It was, but it was a phone from an Australian carrier Telstra. It still had the first version of Android on it, and no updates available. Release software (Android 9 and OneUI 2 I think it was).