https://make.wordpress.org/core/2020/02/13/an-updated-button-component-in-wordpress-5-4/

<IconButton/> has been deprecated and can be replaced with <Button icon> eventually. I don't think there's hurry but just wanted to have this on record so that we don't miss it.

There are quite a few: https://github.com/Automattic/jetpack/search?q=IconButton&unscoped_q=IconButton