These are the BLs involving Taoism that I have identified so far.
Taoist BL series – Complete list?
Untamed – Full of Taoist ideas.
Stay by My Side – His sister runs a Taoist Temple.
Century of Love – It is a Taoist temple.
Komorebi – The protagonist marries a man who runs a Taoist temple.
An episode in Tonhon Chonlatee when they visit the Taoist temple Chao Mae Sam Muk. Episode 8 Part 1.