I think the most direct competitor to discord (for gaming and related communities) is guilded.gg which is basically a clone of discord that offers additional features as well, including offering most of the features that discord has paywalled behind "nitro" for free.

The big issue they have is building up a large enough network effect. I really can't see the discord communities I am a part of moving over there any time soon. Also, they were recently acquired by roblox, and nobody knows for sure what the new ownership will end up doing to the platform.