CloudFlare Tunnels (cloudflared) or Tor are always options to exposing a relay. i2pd too, but the network is kinda... all over the place. Needs more nodes I fear. Still, doing Nostr hosting is ridiculously easy. Everyone can be a "Nostr Service Provider".
nostr:note1cp5ku5vjhzlwyjztwncm9hqzwzjm0ra5r2zqp754ptmlym8m9y3slhvcl4