Hello, I'm not sure which part of the LGBTQ letter crowd you're from, I'll just assume you're the G since someone recommended you to the Red House, sadly in Taiwan the LGBTQ crowd does not mingle as a whole but rather separately.
The Red House, or Ximending in general, during the day it is filled with junior high school kids, but at night the outdoor plaza is filled with men.
There's a LGBTQ bookstore called Gin Gin Bookstore, and about two doors away there's H*ours Cafe, a coffee shop with plenty of happy gay men every time I passed by.
I once been to a supposedly LGBTQ-friendly coffee shop near Shi-Da nightmarket called 米倉, but even with that giant rainbow flag hanging next to the door, all the patrons inside looked really straight to me, even at night.
Sorry I cannot be more helpful, but you can try the Taiwan Tongzhi Hotline, I believe they do provide such information, if you can't speak Chinese fluently ask a friend to call in for you