qBittorrent 4.2.0 was released recently featuring support for libtorrent 1.2, some minor new features, as well as WebUI updates.
qBittorrent is a free and open source BitTorrent client for Windows, macOS, OS/2, Linux and FreeBSD, written in C++ (Qt) and Python (for its optional search engine). It comes with a Qt GUI, but it can also be used on a headless server, without requiring the X window system -- in both GUI and headless mode you can remote control it through its web user interface.