Replacement for Supercard in Catalina? I have been a long time Hypercard fan. When Apple mysteriously dropped it, I kept my Hypercard stacks going using Supercard. Unfortunately, Supercard is not 64 bit compatible (and no sign that that is going to happen any time soon), and so will not run under MacOS Catalina.
Many of my Hypercard stacks are really just fancy Address books, and I could export them to Apple's Contacts app. 

However, I have a more sophisticated complicated stack that is really like a  little customer database ... 

My Question is:  Are there are any free or simple (but good) apps that you would recommend for that purpose:  one card per person, usual entries for email and contact information, and then which version of the software they are using and similar. Simple database or even simpler than that might suffice. All suggestions appreciated.
LibreOffice contains a database application, Base. There are several available Address Book templates, which you could modify.

(I note that SuperCard are blaming Apple for 'going back on their promise to release a 64-bit Carbon framework'. A 64-bit version was noticeably absent in 2007, and Apple deprecated Carbon in 2012...)