On KDE Neon with the Snap backend installed, packages available as Snaps always appear as installed, even when they are not installed. They show the options to Remove the package from the listing view, or from the description view, the option to Remove or Open. The Open button does nothing. The Remove button prompts for authentication, then shows the error, "snap [package-name] is not installed".
*** This bug has been marked as a duplicate of bug 390482 ***