If one looks at an app in the store, there’s the section downloads, which albeit not declared as such, shows if an app is considered compatible or not with a particular nextcloud version. So if I see downloads only up until version 26 and I’m running 27, I know I’m on thin ice.
Similarly, if I see a download for version 27, I assume, it should work.
However, where I would love to see this, e.g. as “Nextcloud version X supported” or “Nextcloud version X not supported, last supported version Y” would be within settings/apps/ when clicking on an app to get the details/inspector side bar.
After upgrading from one version of NC to another, this would be very helpful to ferret out potential trouble makers.
I’m sorry I don’t get the point… Apps in the app store ships metadata and supported version are listed there… you can see supported versions as well: