I’m not 100%, but I think there is a way in still around the back. How to get around the back is beyond me since I haven’t been. But it’s what I heard.
It’s not mentioned on the list, but there is an abandoned temple in Taoyuan which is worth checking out. It is halfway up a hill, to the north of the city.
This site says it is closed because of heavy metal pollution. However, there are spots you can go to take a photo of the place, just not inside the place.
If we’re serious about including all Taiwan, what about some of the extraordinary slate architecture in some abandoned Paiwan villages in Pingtung such as Tjuvecekadan?