As far as I can tell the main sites I use like chess.com, lichess.com, and chess24.com do not support bughouse. Is there a popular place to play online somewhere? It would also like to have the ability to play on iOS. Thanks.
use one of the fics interfaces. Freechess.org
You can play on online1.eu where is possible to play slower bughouse also. There You play using web browser, so You can play from any PC, notebook, tablet, iPod etc. with any operating system like windows, linux, android, or iOS.
FICS(freechess.org) and ICC(chessclub.com)
Android mobile app for bughouse online game with your friends: https://play.google.com/store/apps/details?id=ru.mail.park.bughouse
chess.com has bughouse; it works quite well.
I know lichess is working on it.