Hi mastro.al,
Thank you for participating in the Apple Support Communities. We understand you're having an issue assigning apps to spaces where you're seeing the "none" option checked. This article explains more about this: Work in multiple spaces on Mac.
"Assign apps to spaces
If you use two or more spaces, you can assign an app (or System Settings) to a specific space so it always opens in that space.
- On your Mac, Control-click an app’s icon in the Dock.
- You may need to first open the app to show its icon in the Dock.
- In the shortcut menu that appears, choose Options, then choose one of the following:
- All Desktops: The app opens in every space.
- This Desktop: The app opens only in the current space. If you use the app full screen, it appears in its own space.
- Desktop on Display [number]: The app opens in the current space on a specific display (if more than one display is available).
- None: The app opens in whichever space you’re using at the time.
By default, when switching to an app, the desktop automatically switches to a space that has open windows for the app. For example, if you create a new TextEdit document in Desktop 3, but TextEdit windows are already open in Desktop 2, your new document opens in Desktop 2. To change this setting, choose Apple menu > System Settings, click Desktop & Dock in the sidebar, go to Mission Control on the right, then turn “When switching to an application, switch to a Space with open windows for the application” on or off."
We hope this helps.
Take care.