Thanks. Indeed, one of my reasons for switching to Mac was precisely because I trust the macOS to be more secure than Windows... I'm still getting used to how this new universe works.
I've just seen on the Alfred main page that "Alfred 4 for Mac is Developer ID Signed and Notarised." This, together with the kind replies from you and Deanishe, has done enough to satisfy me!
Now I just need to decide if to get the Mega version. How often do new versions come out, and do they render previous ones obsolete? I get the feeling that I might get hooked and become dependent on some of the functions, so I'm ok with investing for the long-term if necessary.