ethane

You're correct that you can't just go to one community on one instance and see every new technology discussion that is taking place on Lemmy, but you CAN subscribe to all of the technology-related communities on different instances and scrolling through posts of communities you're subscribed to will show you all the discussions you want to see.

Ideally yes, but for a more niche community, federation is slower and posts don't get pushed through. I can see a lot of confusion when someone creates a niche sub because they thought it didn't exist, when in reality it does, and they were just the first to search for it from their server.

Oh how do you do that auto federation thing?

The best chance of succeeding is federation across both. The user base on both is already small, there's no need for this us-vs-them mentality.

But any site which restricts sign ups is going to turn off 50% of the people who show up.