It's not available now for your's device. Always a Stable Version Update is better than the Beta Version Update. So please don't bothered about this issue now. You will be get One UI 8.5 Stable Version Update maybe in this quarter. If you like please accept it's as a solution it's help to other users also, click on 3dots in my reply section and click on accept solution. Thanks.
As per your query, we would like to inform you that as for now there is no official information available about UI 8.5 update for Z Fold5 series. Please stay active on the Samsung Members application, as you will be notified when it becomes available for your device.
