The old dell latitude will be perfect. Ubuntu is fine. It'll already have everything you'll need to run any of these nostr relays. You'll need nginx installed or nginx proxy manager if you prefer a web interface to organize your SSL certificates.

When setting up the proxy, remember to turn on the websockets option in nginx because all connections to nostr relays are done via wss:// connections. Only the simple web page that most have to describe the server are delivered over https.