A handy list for this day and age - alternative social media platforms - Synthstuff

Social Media and Online Communities
A List of Alternatives for Social Media and Online Community Platforms

There are three main categories for social media alternatives:

- Centralized - Structured in a way that gives one authority complete control of every aspect over a platform. Big Tech social media companies tend to be shaped this way. The downside to this structure is if the people that run the company happen to be corrupt, you are forced to tolerate their crappy policies.
- Decentralized - Distributed software service hosted by different groups and individuals rather than being stored at data centers and facilities controlled by one corporation. The software is free and open source which enables anyone to host an instance of that service. Offers an ad-free, algorithm-free, private and transparent experience. You can not only communicate with people within the instance but the entire network. Only exception being instances that are blocked by the admin.
- Front-End Mirror - A community-hosted (typically also includes an option to self-host) proxy to a big tech site that lets you connect to and browse a big tech site without being subject to tracking or malicious javascript.

Pretty comprehensive. Some link rot, some really interesting sites.

A handy list for this day and age - alternative social media platforms