There are broad resources for many different use cases like Fediverse Party — covering many different forms of social media. But I present the simplest options for exit today that don't require a complex setup. This provides an easy way to get in without having to go deep on the federated wiki iceberg.
Servers may seem confusing at first. Most open source applications have general purpose servers for broad communities. There are also local servers for your state or specific interests.
This is the magic of federation: you can see users across different servers while staying on your chosen instance.
Exiting does not have to be immediate. One can operate simultaneously on centralised platforms while also taking part.
The Digital Justice Society (Kaurna Yarta / Adelaide) have resources for Spotify alternatives:
If you have an old laptop lying around, you can make do with self-hosting. But the minimum viable exit for your capacity right now is more than enough. Try to get your friends to join you off platform.