SetupFixedDeltaTime.cs

public class MyController : MonoBehaviour
{
    private void OnEnable() {
        SetupFixedDeltaTime();
    }

    private void SetupFixedDeltaTime() {
        var xrSettings = XRGeneralSettings.Instance;
        if (xrSettings == null) {
            Debug.Log($"XRGeneralSettings is null.");
            return;
        }
        var xrManager = xrSettings.Manager;
        if (xrManager == null) {
            Debug.Log($"XRManagerSettings is null.");
            return;
        }
        var xrLoader = xrManager.activeLoader;
        if (xrLoader == null) {
            Debug.Log($"XRLoader is null.");
            return;
        }
        var xrDisplay = xrLoader.GetLoadedSubsystem<XRDisplaySubsystem>();
        if (xrDisplay != null) {
            if (xrDisplay.TryGetDisplayRefreshRate(out float refreshRate)) {
                Debug.Log($"Refresh Rate: {refreshRate}hz");
                float nextFixedDeltaTime = Time.timeScale / refreshRate;
                Debug.Log("Setting fixed delta time: " + nextFixedDeltaTime);
                Time.fixedDeltaTime = nextFixedDeltaTime;
            }
        }
    }
}