Nice route! Used to be a road connected from Zhiben side through to Jingzhenshan, but was always a bit sketchy
Our goal was to see q
...whether that could be done. This was the fourth attempt. Didn't find a passable route to go all the way. This was our most complete. Good fun trying to find a way.
The road starts from 知本溫泉， past 弘溫泉hotel, (looks like you were on it) then just follow the road , don't take any turnoffs to 藥山， road deteriorates after about 6-8km if I recall but was passable and connects with the back road from 太麻理to 金針山（via真興village)at about 600-700m altitude. Maybe it's washed out now, I last did it about 10years ago, remember lots landslides and bike portering whereas before then the whole thing was rideable (but hard!). If you need info on any mountain road/trail from Taimali to Luye ask, I know them probably better than anyone, doing it for29 years!.
Thank you, I appreciate that