WordPress adds “noreferrer” to all links that open in a new tab. This started before Gutenberg and a TinyMCE filter was provided to fix it. This no longer works for Gutenberg. They have a new wp_targeted_link_rel filter too that only works for the classic editor.
I manually removed it from all my links and all was fine on WP 5.0. Upon updating to WP 5.1 it was added back to all of my links after updating the posts. This is a nightmare.
The reason to remove it has to do with tracking the originating domain with affiliate networks. Even those that use affiliate ID’s as URL parameters still demand that the referrer be an approved domain.
Has anyone found a way to stop this on Gutenberg yet?