The analysis engine in the new Lichess app has given me some problems. However, restarting the app and checking the same analysis always fixes it for me.

edit: Actually, nevermind. That analysis is truly borked. You should report it, so the team can have a look.

edit2: Gods! it's well and truly goofed. It isn't even this game. You can just go to the analysis tool and play: 1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5, and it switches to #1.

Seems broken. It claims "if black moves a6 or b6, then Nxf7" is mate, but it is not even check.

White bishop from C4 to F7 is mate.

Your king can't take the f7 because the white horse is covering that tile too.