Read 24 Vac signal with a Raspberry Pi
Instead of using a slightly larger number of inexpensive multiple-sourced parts, you could consider using a part designed for this kind of application, the TI ISO1211.
See Figure 3. I think values of Rsense = 560 ohms, Rthr = Rshunt = 1K and C = 100uF/50V would work, but check that yourself. It will run off the 3.3V Pi power supply.

You might want to use a bridge rated at a bit higher voltage.