Trying to figure this out as in the recent threads a few people said that Bluesky was federated, but it didn't seem to actually be the case.
https://bsky.social/about/blog/02-22-2024-open-social-web in February announced that Bluesky would allow federated servers
The Bluesky documentation on the topic isn't very clear. They mention Bluesky.social a lot, as if it's supposed to be the one central server other PDS need to federate with:
Bluesky runs many PDSs. Each PDS runs as a completely separate service in the network with its own identity. They federate with the rest of the network in the exact same manner that a non-Bluesky PDS would. These PDSs have hostnames such as morel.us-east.host.bsky.network.
However, the user-facing concept for Bluesky's "PDS Service" is simply bsky.social. This is reflected in the provided subdomain that users on a Bluesky PDS have access to (i.e. their default handle suffix), as well as the hostname that they may provide at login in order to route their login request to the correct service. A user should not be expected to understand or remember the specific host that their account is on.
To enable this, we introduced a PDS Entryway service. This service is used to orchestrate account management across Bluesky PDSs and to provide an interface for interacting with bsky.social accounts.
https://docs.bsky.app/docs/advanced-guides/entryway#account-management
Self-hosting a Bluesky PDS means running your own Personal Data Server that is capable of federating with the wider Bluesky social network.
https://github.com/bluesky-social/pds?tab=readme-ov-file#what-is-the-current-status-of-federation
The custom domain name is still something else, and does not seem to require a PDS: https://bsky.social/about/blog/4-28-2023-domain-handle-tutorial
So, to come back to the title question, do people know of an example of PDS that can be used to access Bluesky without being on the main server?
There are some people hosting their own identity server, but yes the centralisation of the main aggregator server seems to be by design as they even scare people away from trying by talking about the high resource requirements of doing so.
IMHO Bluesky is only federated in the sense that responsibility for content and moderation can be outsourced, but the user endpoint stays mostly in control of Bluesky. This makes a lot of sense if you think about it from a company perspective... outsource the legally and personnel critical parts and keep the ones that are lucrarive for advertisement and can be easily scaled by throwing hardware at it.
But you must be a real sucker to take them up on that very one sided offer...