I'm wondering if there's a plugin that allows people to type in f.ex. "/Discord" and they'd be sent a link to my discord group? As of right now I've only found chat notifiers and other more advanced discord plugins, but not what I'm looking for.

You could use SmartChatBot plugin

https://umod.org/plugins/discord-core + https://umod.org/plugins/discord-chat

The fastest and easiest way would be

https://umod.org/extensions/discord
+
https://umod.org/plugins/rustcord