I am creating a pull request for this. I have successfully built on a machine running Gentoo Prefix.
Version 22.0.2 got added some time ago: commit f2c6efc25875aed7e2ef3c0f57ed03fb03c2cc81 Author: Anthony G. Basile <blueness@gentoo.org> Date: Tue Jun 4 13:23:29 2019 -0400 dev-lang/erlang: version bump to 22.0.2 Signed-off-by: Anthony G. Basile <blueness@gentoo.org> Package-Manager: Portage-2.3.66, Repoman-2.3.11