In mentioning stable, I guess I was really drawing your attention the the fact that I think you have a Samsung which has been “stuck” on Oreo for many users until the Over The Air Upgrade to Android 10 arrived; I think it was introduced here OS OTA Upgrade of S9 / S9+ . There is useful information there including further background on build types; you can follow the story of the roll out as it was posted weekly in #development-updates.
You can find the build description in Settings > About phone > tap on Android version > /e/ version. Sometimes you can long press on /e/ version to copy to clipboard.
I am sorry, I cannot really offer an explanation why an Update has not been offered if you have it enabled. You probably already checked Settings > System updates > top right menu, Preferences and checked you have regular check enabled (it is possible to disallow it with ‘Never’ !)