@usersqIcB23JEx I know the One UI 2.1 just started it's release so you should get that soon.
It looks like the Samsung Note 9 is getting updates in a phased release. Depending on your version, carrier, and country of origin that timing may vary. You can read more about the roll out here from a non-official source. Once the update is available you'll see it applied via Settings over the air. Make sure auto-update features are enabled for your device.