qBittorrent is a bittorrent client programmed in C++ / Qt5 that uses
libtorrent (sometimes called libtorrent-rasterbar) by Arvid Norberg.

It aims to be a good alternative to all other bittorrent clients out
there. qBittorrent is fast, stable, and provides unicode supports as
well as many features.

Note that from version 3.3.15 you will get a warning on startup that
qbittorrent has a new way of saving things. If you want to backup your
old config directory first, you will find it here:

~/.config/qBittorrent

You can return to an older version by swapping directories around.