Install this version:
emerge -a =app-emacs/tramp-2.8.1.3
If this version is masked, you can unmask it using the autounmask tool or standard emerge options:
autounmask =app-emacs/tramp-2.8.1.3
Or alternatively:
emerge --autounmask-write -a =app-emacs/tramp-2.8.1.3
# automatically generated by g-sorcery
# please do not edit this file
EAPI=8
REPO_URI="https://elpa.gnu.org/packages/"
SOURCE_TYPE="tar"
REALNAME="tramp"
DIGEST_SOURCES="yes"
inherit g-sorcery gs-elpa
DESCRIPTION="Transparent Remote Access, Multiple Protocol"
HOMEPAGE="https://www.gnu.org/software/tramp/"
SRC_URI="${REPO_URI}${REALNAME}-${PV}.${SUFFIX}"
SLOT="0"
KEYWORDS="~amd64 ~x86"
DEPEND=""
RDEPEND=""