I tried to emerge  net-im/telegram-desktop
but it said:

emerge: there are no ebuilds to satisfy "net-im/telegram-desktop".

emerge: searching for similar names...
emerge: Maybe you meant any of these: net-im/telegram-desktop-bin, net-misc/grdesktop, net-im/mattermost-desktop-bin?

I'm not interested in the binary version.  There's this:

https://packages.gentoo.org/packages/net-im/telegram-desktop

I tried adding this to /etc/portage/package.accept_keywords because the newest versions are shown in yellow:

net-im/telegram-desktop ~amd64

but it didn't help.

Can I emerge this as source?