Good question.
I did find one rather dated solution (11/17). Actually, there are three "temporary" and one "permanent" solutions. This will only apply to Apple software, of course. The permanent one requires accessing the System Prefs->App Store. However, you probably don't have that in System Prefs, I certainly don't with
Mojave macOS 10.14. However, you
do have one called "Software Update". In there, the key pref is "Check for updates". Make sure that is
UN-checked.
The only other item in that Pref that I use is the "Install system data files and security updates". That's not what I did before Mojave. I've decided security updates are more important and even
problem-causing security updates get fixed pretty quickly and are rather rare.
Hope that helps.
You might also try scheduling "Do Not Disturb" in the Notifications System Pref. Basically, if you have the Mac running on a schedule or you simply turn it ON/OFF regularly, you can set that time period in the Notification Pref. That will stop ALL notifications during that time period.
If you are still getting notifications about a specific 32-bit app, you may be able to select it in the list of apps on the left-hand area of Notifications prefs and Select "None" for style and UN-check all the checkboxes.
If none of these methods work, I suggestion a piece of opaque tape in the Notifications area os the screen. Duct® tape comes in many colors. Hopefully one will go well with your Desktop image.
