The following packages are for grabs:

net-im/telegram-desktop
media-libs/libtgvoip ( no other revdeps )
media-libs/tg_owt ( no other revdeps )
dev-cpp/range-v3 ( has another revdep, not only tg )

Many bugs open and many issues.

Before you try to take it over, here's some info for future maintainers:
0. you better speak Russian to be able to reach devs =) optional, but VERY beneficial. I can connect you to developer group.

1. expect to deal with a lot of bundling, no releases, submodules and all related packaging issues with this approach.

2. expect pretty aggressive userbase, very direct, even brutally so.

3. expect dependency fights between wayland-only crowd and x11-only crowd.

4. same as above but for pulse vs alsa.

5. same as above but openssl vs libressl (this one should be easier nowadays as support is going away)

6. project is split into 4 repos basically, 1 for app, 1 for webrtc, 1 for cmake files, 1 for audio lib. there are no releases for any except tdesktop itself.

7. expect to read a lot of cmake cross-referenced across all those 4 repos.

8. expect to be able to patch cmake a lot. for example one can't toggle off automagic deps.

9. expect to collaborate with other disto developers, who also work on mentioned tasks. rpmfusion and freebsd guys are very helpful and solve same problems as we do.


If you are still reading - reach out, I'll help to get started.
I don't have time to maintain it anymore, so it either should be removed or go into caring hands, as it needs A LOT OF CARE.

https://bugs.gentoo.org/buglist.cgi?quicksearch=telegram-desktop
-- 
Best regards,
Georgy