TrackIR 4 with software version 5.4.2 works fine for me in 2024. Make sure the TrackIR option is toggled on in the camera menu from the toolbar (it was by default for me).
I didn’t actually manage a flight yet as I’m stuck in the floor in walkaround mode after loading in, and I can’t even get into a plane, but I can look around with TrackIR from my vantage point below the ground… at least that’s something!