@mathowie Ah, I get it:
1) Schedule an appointment.
2) Choose flu shot.
3) There's a notification that, while you're they're, they'll give you a COVID vaccine if they have one (which they should by the time of the soonest appointments, a couple of weeks out).
This appears to work via either web or app.
@mathowie I also tried the app and don't see a place to "schedule a flu shot".