What firmware and firmware version are you currently on ?
May I ask what's "rubbish"
In my opinion their isn't much more in Oreo to Nougat.
Your phone should let you know automatically when an update is available.
You can manually check if an update is available by going into Settings-Software Update-Download Updates Manually.
Side Note > if your phone is branded ie been supplied by a network as part of a contract end then it's up to that network usually to test firmware before it's sent out by Samsung.
Firmware is sent out in batches typically based on the phones date of manufacture and serial number.
Neither Samsung or the networks will comment on firmware update timeframes.
Current Phone ~
Samsung Note 20 Ultra 5G SM-9820 _256Gb SnapDragon 865+
Samsung One Ui 2.5/ Android 10.