Most clients try to set up port forwarding using UPnP IGD, NAT PMP, or PCP protocol, a lot of residential routers support one of them. If you enable WebTorrent

Most clients try to set up port forwarding using UPnP IGD, NAT PMP, or PCP protocol, a lot of residential routers support one of them. If you enable WebTorrent as a transport protocol (enabled in gotorrent, disabled by default in libtorrent), it should be possible to use existing public STUN/TURN infrastructure, but I don't know if any client does it yet. In practice, you just have to accept that many connections will simply fail, and make your client move on to try a different peer.