Here is a list of Discord Integration addons that can be installed no matter the modloader or mc version you are on. Most of them will very likely require Java 17 tho.

• Voice Notifications - Send messages when someone joins/leaves voice channels to minecraft
• Exec Command - Adds an /exec command allowing to run any console command you choose
• MySQL - Adds MySQL database support

There may be more which are not listed here, try searching with this tag: https://github.com/topics/discord-integration-addon

Here is a list of mods / plugins that directly extend Discord Integration

• Forge
  • MineMineNoMiRoleAssigner 1.16.5 - An Addon for Mine Mine no Mi that synchronizes your character stats with Discord. Currently needs to be compiled yourself