The "Taking iPad apps for Mac to the Next Level" talk at WWDC 2019 has a fantastic overview of all the changes. Here is a brief overview:
UIApplicationlifecycle is fully supported on macOS
- The sequence is the same as on macOS
- State changes, however, do affect the Mac less, as are almost always Foreground + Active on macOS.
- Apps only enter background during termination and inactive when launching in the background.
- Your app should still take App Napp into account
- Background modes are allowed to finish when an app closes. The background tasks continue even though the app is already not visible anymore to the user
- Apps are not killed when they consume too much memory
- Background audio is not supported because users expect audio to stop when they quit an app
So, in short, your app is always in
Foreground + Active except when it is (mostly) launching or terminating.