An absolute shit tonne. 
Anal play itself has nothing to do with sexuality. Lots of straight guys love it, either by themselves or with a partner. It’s just an area that’s jam-packed with nerve endings and, of course, the prostate.
If you throw a butt plug in any direction you’ll hit about 1000 topics on it. This one is a good one: Pegging. Male pride confidence boosting thread. (it’s a pegging one, but the theme is the same )
And here are a couple of guides you might find interesting:
Beginner’s Guide - Anal Sex Toys
Butt Plugs
Prostate Massgers