Currently, IMO, the easiest way is to install a prune Bitcoin Node (150 GB of space minimum) Umbrel OS, once completed go the app store and install NISTR Relay. Very low level entry with little to none knowledge required

The cons:

1. No relay filter control in current version

2. No remote access unless you are familiar with Tailscale and port forwarding, (medium low level)

3. Remote access over TOR does not work yet on Amethyst or Damus (the clients hopefully will enable TOR connection in the future, NOSTR is a privacy nightmare, your IP is in several relays with all your notes pointing at it..., use always a VPN meanwhile), haven't test Snort and Iris web versions

You can avoid the Umbrel installation and adquire Star9 box and do the same, but my understanding is that you have an old hardware you can put to good use, so Umbrel is a fair game