I might try Friendica, although coming from lemmy I’d be more inclined towards Mbin, to combine topic-focus and people-focus.
However as a developer I first check the code repos and see that both are based on php, which seems rather old, and i doubt this would scale efficiently if the network really took off. Recall that twitter was once based on ruby (like mastodon is) and shifted to scala for such reasons. So I feel, these are exploring well the potential user-experience, but the code may need a fresh structure (if somebody knows this tech issue better, please say). It’s good to discuss these things, to help consolidate potential efforts.
This is hardly surprise news, it’s just what the demographics projected. And if trends continue, China’s population will halve by 2100. The big one to watch now is India, and then central Africa, those are harder to project.
You can experiment with my model - click the ‘model pop’ plot on the left side.