I’m fairly sure I’ve seen an NNTP based imageboard that distributed it’s content through that protocol and different instances had overlap of boards. That’s about the closest match to federated system you’re going to find with this model I think. Interesting concept. Not something I’d want to interact with personally though.

Certainly not as powerful as common office suites, but https://cryptpad.fr/ is not only open-source but also has already running instance (and has end to end encryption for your documents)

https://syncthing.net/ is a good general file synchronizer. Requires devices too be online simultaneously to sync, but gives you transport encryption with forward secrecy.

It’s probably the best one when it comes to web-based videocalls. I had much better experience with native apps (e.g. Mumble) when it comes to sound quality though.

Re profiling, I don’t think instances will bother doing that (unless they start running ads). However, they also don’t prevent anyone from building that profile themselves from observable behavior. And creating such database might constitute original work by itself. Now, they don’t get as fine-grained interactions as you would with tracking-infested sites. But they will get the most valuable ones such as active participation.

One thing I’d love to see and would probably help quite a lot with searchability is to have blog and CMS software, instead of having dedicated comment system, integrate a “discuss on Fediverse” button.

It could bring up possible communities based on blogpost/article tags. And since Lemmy supports pingbacks the system would know about the discussion threads and it could even show few last posts from each.

To me it seems like win/win situation for all parties involved.