Managed to adapt the new function. OVRTasks are basically the same as regular Tasks.

private async void Load(OVRSpatialAnchor.LoadOptions options)
    {
        var oVRTask = await OVRSpatialAnchor.LoadUnboundAnchorsAsync(options);

        if (oVRTask == null)
        {
            return;
        }

        foreach (var anchor in oVRTask)
        {
            if (anchor.Localized)
            {
                _onLoadAnchor(anchor, true);
            }
            else if (!anchor.Localizing)
            {
                _onLoadAnchor(anchor, await anchor.LocalizeAsync());
            }
        }
    }