I was there recently.
My hotel was near Linsen Road.
I noticed there was a few massage places on Linsen Road on Google Map.
Next thing I sent a few Line messages to them and was told to go to a particular building and floor.
It's all very secretive, but once you tell them you are from HK, they are usually quite welcoming.
Doors are heavily bolted and locked, but they will allow you in and then the fun starts.
Usually a lineup of 10-20 girls, costing 2500-3500TWD for massage fees.
Once you pick the girl and inside the room, you get a typically naked body to body HJ.
Girls usually try to upsell you with additional services. They all quote slightly different rates ranging from 1000-4000TWD.
There are 5-6 of these establishments all around Linsen Road from a couple of different operators.
They will point you to their sister shops. Different lineups, different girls during different times.
Also tried the agent delivery to hotels at 8-10k. They were ok, but pictures typically don't match the real person.
I prefer to choose from lineup.

Thanks for the valuable information!

How do you find the LINE contact too message?

Wait, it cost 3500 TWD for a HJ and upsell for more? Should have just gone to a 24 hour sauna instead.