[fleg]

For what it's worth, Ripcord[1] can do that (okay, it can open channels in separate tabs that can be moved to separate windows). And it is a native (Qt) application.

The only problem is that it's not free (with unlimited trial, though) and the development seems to have stopped. Still works okay for text chat, though.

[1]: https://cancel.fm/ripcord/

[tumult]

Not stopped. The next update is being worked on.