From my perspective mails are federated. If I want to explain federation as a concept to someone I always use mail as an example because everyone can write to everyone independent of the provider, you can selfhost it easily, you could move from one company to another (if you use your own domain), protocols are all FOSS.

So at least it’s an open and distributed system. What would be missing for it to count as federated?

I’ve always missed a rating/feedback/comment feature in F-Droid. A lemmy-based solution would be pretty cool.

Can you reach the server’s IP in general from other PCs in your network? Or is the issue restricted to the nextcloud service?