I have Mojave. I found that I can silent all notifications if I go under notifications and specify do not disturb all day. However I think this also means that I will not get any important notifications. I'm fine that this particular machine being hacked, exploited or whatever, seriously, I just don't need updates on this particular machine. Or at least warn once a month, not every 24 hours. On windows and linux its 3 clicks, is Mac capable of something like this?
Here are some things you may try:
This site offers a solution by going to System Preferences, Software Update, De-Select "Automatically keep my Mac up to date".
Alternatively, try going to System Preferences > App Store > De-Select "Automatically check for updates"