Careful with the broken tag, it will break.
I would consider muting all categories by default, and prepare topics tagged #welcome to give an overview of available categories. When you associate a group to watch a category, then you can create a progressive experience, where people can join groups to unmute/discover categories. With a very few welcoming topics, you can provide readers with an overview of what’s available and give them the choice where they want to participate. Documenting notifications is also important to avoid information overload.