I installed Deluge 2.0.3 on Lubuntu 18.04 from the official repositories today (there is no Windows port yet, and I don't have the time to compile one), and its announces look like this.
Code:
GET /announce?info_hash=%84%b8%b8pm%7f%c5%bb%c1%93%f2%5d%8b%24%19~%dce%a2%fd&peer_id=-DE203s-JVXJE2-zYA8M&port=54143&uploaded=0&downloaded=0&left=790626304&corrupt=0&key=EEB6FF6B&event=started&numwant=200&compact=1&no_peer_id=1&supportcrypto=1&redundant=0 HTTP/1.1
Host: torrent.ubuntu.com:6969
User-Agent: Deluge/2.0.3-2-201906121747-ubuntu18.04.1 libtorrent/1.1.5.0
Accept-Encoding: gzip
Connection: close
Note how when compared against the template in the first post, the peer_id prefix ends with "s" ("stable"?) instead of "0", and the User-Agent is expanded with additional version information. Can anyone confirm these changes on other distros, or perhaps an unofficial Windows port? This sort of thing makes it impossible to write client emulations that are safe for everyone.