Is there any way to run incompatible apps from future versions of macOS?
In a word, No

There are differences in macOS versions, and if an app says "macOS Catalina or later" it means that it requires something that is specific to, introduced in and not in earlier versions of macOS.

For example if you have an app that requires macOS High Sierra or greater it will also (likely) work on Mojave and Catalina too, but not on Sierra.

So, sorry, but that app was written to use a feature of Catalina that is just not there in previous versions of macOS.

You could contact the developer and ask if it is possible but I would bet no.