It's also my experience that Fedora has better support for it, but Gentoo used to be good enough with hardened gentoo (they use https://gitweb.gentoo.org/proj/hardened-refpolicy.git/). Redhat and Gentoo are the only ones that officially support it afaik. I think hardened gentoo might have lost popularity since the fall of grsec, but I'm not sure how popular it is currently.
It's also my experience that Fedora has better support for it, but Gentoo used to be good enough with hardened gentoo (they use https://gitweb.gentoo.org/proj/hardened-refpolicy.git/). Redhat and Gentoo are the only ones that officially support it afaik. I think hardened gentoo might have lost popularity since the fall of grsec, but I'm not sure how popular it is currently.