Best Minecraft: Java Edition Discord Servers

Most Minecraft Discord servers exist to support a game server. The Discord is where you apply for an SMP whitelist, read the rules, report griefing, see restart and map reset announcements, and coordinate builds with the people you actually share a world with.

The rest are communities in their own right: modded Fabric and Forge pack servers, redstone and technical Minecraft help, build showcases and world downloads, and general MC chat covering both Java and Bedrock. Search terms like mc or minecraft java land here too. Check which edition and version a community runs before applying, since that decides whether you can join at all.