For your use case, here is what I would recommend:

Hardware: A used mini PC (Lenovo ThinkCentre Tiny, Dell OptiPlex Micro, HP ProDesk Mini) from eBay — around $80-120 for an i5 with 16GB RAM. Way more power-efficient than old tower servers (10-15W vs 100W+), dead silent, and plenty powerful for everything you listed.

Add a USB 3.0 external drive dock or a small NAS for the storage. For ~3TB total, a single 4TB drive is fine to start.

Software stack:

• Immich for photos — absolutely the right choice, it is incredible
• Jellyfin for media — correct again
• Navidrome for music — perfect pick
• Calibre-Web (not Calibre itself) for ebooks — much nicer web UI
• Syncthing for file sync — simpler and more reliable than Nextcloud for just file syncing. Only use Nextcloud if you also want calendar, contacts, etc.

The glue: Run everything in Docker with Docker Compose. One docker-compose.yml file, one docker compose up -d, and you are running. Use Caddy as your reverse proxy — it handles HTTPS automatically.

Don’t overthink it. Start with one service (Jellyfin is the easiest win), get comfortable with Docker, then add more. You will learn more from running things than from planning.