I would also recommend lemmy. It’s more established, has a strong community footing. And above all, it seems to be well written (in terms of code) and has tons of clients (UIs/apps). And like the other comment says, I’m not convinced about the performance of piefed

Maybe LibreOffice Draw can help you out? It has PDF editing capabilities

This is very interesting, could you please elaborate a bit? Are fathers not involved in parenting in traditional Japanese culture?