Let me introduce myself first. I am a member of KDE Promo group and the guy behind Plasma release videos. I was also involved in making Kubuntu 15.10 release video.
http://www.kubuntu.org/news/kubuntu-15-10/
Given the recent changes in the Ubuntu I think that Kubuntu have a great opportunity to become more visible. One of the ways to do this is by shipping high quality applications. This task is only meant to spark a discussion.
**Music player**
Amarok - no longer maintained, no port to kf5.
Alternatives:
Babe: https://phabricator.kde.org/source/babe/
Elisa: https://phabricator.kde.org/project/view/193/
Cantata: https://github.com/CDrummond/cantata
Qmmp: http://qmmp.ylsoftware.com/
Clementine: https://github.com/clementine-player/Clementine
**IM client**
KDE telepathy - unmaintained
http://martys.typepad.com/blog/2016/06/new-maintainers-wanted-kde-telepathy-kaccounts-plasma-notifications-and-others.html
As a matter of fact it seems that Empathy and telepathy are in similar situation.
https://mail.gnome.org/archives/release-team/2015-April/msg00050.html
Telepathy doesn't work with most most popular chat protocols which are mostly closed nowadays.
The only alternative I can think of is Telegram which is quite popular among KDE users (open source client, closed server side)
**Torrent client**
Ktorrent: https://phabricator.kde.org/source/ktorrent/
version in Kubuntu still uses KDE4 libs, however there seem to be kf5 port available
http://shaforostoff.blogspot.com/2015/11/ktorrent-kf5-port.html but kf5 branch isn't too active
https://phabricator.kde.org/source/ktorrent/browse/5.0/
Is it even merged?
Alternatives:
qBittorrent: - https://github.com/qbittorrent/qBittorrent
Cross platform Qt 5 client. Very popular, actively developed.
**Video player**
Dragon player: Very basic and to be honest I don't know anyone using it.
Alternatives:
VLC - http://www.videolan.org/
well known Qt 5 cross platform video player
Smplayer - https://sourceforge.net/projects/smplayer/
Another cross platform Qt 5 player (mplayer, mpv backend). Highly customizable, active development.
**KDE PIM**
KDE PIM or to be more precise KMail is perceived by some of our users as too complicated. Given the fact that more and more users are using web clients shipping KDE PIM by default is questionable. Alternatively Trojita http://trojita.flaska.net/download.html may be a better choice.
Of course this is very subjective opinion.
I know that some of these applications aren't strictly under KDE umbrella, however we should be pragmatic and choose the best application in each category, as long as they integrate with Plasma desktop.
As I said earlier this task is only meant to spark a discussion so any comment/opinions welcome.