While Sentinel has not cottoned to the cat door, Antares has figured out that he can be an outdoor kitty by just pushing through it.
While he doesn’t spend a ton of time on the catio, he does go out every night, and there are even times during the day when I will find him keeping an eye on the front sidewalk.
He might spend more time there when it gets warmer outside.
Side note. The concrete turns green like that every winter. We could spray it off, but why bother? It goes away when things warm up.