How can I tell if a MacOS App is notarized or sandboxed? I'm running MacOS Catalina.  How can I tell if a particular MacOS App downloaded from the Internet is notarized and/or sandboxed?
I'm not sure if this helps but if you open System Information and in the side bar, go down to Software > Applications, you should see all the applications installed on your Mac. Clicking on any app will show you their certificates, version, and where you obtained these applications (i.e. from Mac App Store, Apple, identified developer or unknown).

To access System Information you can open it from a Spotlight Search, or click on the About this Mac in the Apple Menubar, and click on System Report. 

Hope this helps.