Hi.
When I look into the SOFTWARE UPDATES in System Preference (the Apple in the top-left corner), I have the OPTION to select a box which will (left unchecked, will not) AUTOMATICALLY update.
I have mine UNCHECKED so that I will receive a notice about whatever update is now available, but it will not download or install until I manually tell it to do so.
* Currently, I am using Catalina and there is a notice for me to update to Big Sur, if I wish to do so manually. FWIW: I usually wait a month or two from the initial release before installing. Hopefully, any grief the new OS causes will be ironed out by the time I am ready to download and install.
