The following helpers in bin/ebuild-helpers are not defined by PMS. Quote: "[They] are reserved for package manager use and may not be used or relied upon by ebuilds:" - prepall, prepalldocs, prepallinfo, prepallman: These have been banned (i.e. they die unconditionally). - prepallstrip, prepstrip: For some reason, these die only in EAPI 7 and later. Probably should be changed to die unconditionally. Last usage removed from Gentoo repo on 2019-04-14. - prepinfo: Outputs a deprecation warning. Could be banned when bug 899898 is fixed. Last usage removed from Gentoo repo on 2018-11-22. - prepman: Outputs a deprecation warning. Last usage removed from Gentoo repo on 2019-04-14. - portageq: *No* deprecation warning. Last usage removed from Gentoo repo on 2020-07-27.
A branch with the final bans is here (merge after 2023-12-31): https://github.com/ulm/portage/tree/ban-helpers