franz-bin : Free messaging app for services like WhatsApp, Slack, Messenger and many more ( https://meetfranz.com/ )
nheko : Desktop client for Matrix using Qt and C++14 ( https://github.com/Nheko-Reborn/nheko )
rambox-bin : Free and Open Source messaging and emailing app ( http://rambox.pro/ )
ripcord-bin : a desktop chat client for group-centric services like Slack and Discord ( https://cancel.fm/ripcord/ )
Add an ebuild in portage :
The ebuild is now in the portage tree.
You can also use layman : emerge layman then layman -a menelkir
For Paludis use this rsync : rsync://gentoo.zugaina.org/menelkir-portage
If you have a problem : ycarus(-at-)zugaina.org