Private in this context means that it is isolated. If you want it to be private in the sense that it's only for you to use the you just close registrations.

Anonymity and federation are kind of oxymoronic.

This basically shuts my idea down

it's not very difficult to modify the code for something like this.... and closing off registration wont' let anyone else login and create new content form your istance.

Personally the load on the major servers by having one more instance that subscribes to everything is why I think people should back off from creating more than the 1500 instances Lemmy network already has. Delivery of every single vote, comment, post 24 hours a day just so one person can read content for an hour or two a day.

That makes sense for email systems where all that content doesn't have to be sent, but for Lemmy it's a huge amount of overhead.

What is your definition of private?

You can disable registration (so you’re the only user and thus no one other than you can subscribe anything). You can simply not create communities on your instance (and thus no one can post anything). You can federate per normal and still browse anywhere you’d please.

Would that achieve what you’re looking for?

The federation/API end point and the web-ui are entirely independent.

If you want, you can run the federated backend with no web ui at all and use it via mobile apps only.

Or you could put some password protection via the webserver in front of the web ui only.

I used a $2/mth vps and got an instance up in about 5 minutes with ansible. Took longer to pay for the instance and ssh into it than the Lemmy install

If I were worried about it gaining users then I'd just limit access to the UI or do some database maintenance

I run my own instance only me. Make sure you setup reverse proxy right :)