Install this version:
emerge -a =dev-lisp/trivial-gray-streams-20170830-r1
If this version is masked, you can unmask it using the autounmask tool or standard emerge options:
autounmask =dev-lisp/trivial-gray-streams-20170830-r1
Or alternatively:
emerge --autounmask-write -a =dev-lisp/trivial-gray-streams-20170830-r1
# Copyright 1999-2024 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2
EAPI=8
inherit common-lisp-3
DESCRIPTION="A thin compatibility layer between Gray Stream Common Lisp implementations"
HOMEPAGE="https://trivial-gray-streams.common-lisp.dev/"
SRC_URI="mirror://gentoo/a9/${P}.tar.bz2"
LICENSE="MIT"
SLOT="0"
KEYWORDS="amd64 ~ppc ~riscv ~sparc x86"