KDE snaps built by KDE neon need the kde-frameworks-5 snap to be installed before the app snap. There isn't any support in Snap for this yet so probably the best place for it is in Discover. It should check if kde-frameworks-5 is installed and if not install it before the app snap. (KDE neon does install this by default on new ISO installs but that doesn't help existing installs nor other distros.)
I don't agree that Discover is the best place. It would only address the issue for a very small subset of the users. In fact, distros that install snap backend could also get snap to install kde-frameworks-5 in general, especially Neon. The solution is in snap itself. Please open an issue there and I'll be happy to follow up on it.