It appears that I cannot download the good guardians app thru the galaxy store.
It would please me greatly if I don't have to download infrastructure software from an unspecified source.
Are you actually referring to the Good Lock app? I did a search on the Google Play Store and Galaxy Store and found there isn't an app called Good Guardians.
After downloading and installing the Good Guardians Agent from APKmirror, each module has to be downloaded and installed separately as well in order to make the app usable. Never had a problem with APKmirror Samsung. The reason for this is that Good Guardians isn't supported by Samsung Canada so the only way of getting it is through a different source other than Samsung Galaxy Store or Google Play Store.