Something that’s a big issue for the nextcloud community us to keep up with version numbers for all the apps. Often we have to wait months before most common apps are updated to support a new version of NC.
Instead of simply having a min-max supported version for an app, I propose that Nextcloud adopts API feature checking.
When compiling software under Linux it is common to use a configure script that checks if all required features are available before compiling. A similar type of solution could work with Nextcloud. If each nextcloud version has a standard API it should be possible to check if an older app will work.