BiglyBT is the first torrent client to add full support for the BitTorrent v2 specification, including hybrid torrents. The client is far ahead of the curve as the first torrent site has yet to adopt the new specification.
https://torrentfreak.com/biglybt-is-the-first-torrent-client-to-support-the-bittorrent-v2-spec-201011/
https://torrentfreak.com/biglybt-is-the-first-torrent-client-to-support-the-bittorrent-v2-spec-201011/