As of May 2017 there is a new HDN community Discord which will serve as a home for both general fans of the series and speedrunners for the foreseeable future. The Discord aims to be more gameplay-focused than other HDN servers out there with a dedicated room for each game/set of games, though there is still a room for Nep media.

You can use this link to join: https://discord.gg/JPJKHFH

Most of the channels are public. If you're a speedrunner of one or more games in the series you can get a "speedrunner" role to access more administrative rooms such as those for marathon planning and leaderboard administration - just PM any user with the CPU role once you've joined.