I already have an Umbrel, this is just a backup relay with no clearnet connection.

I also experimented with a Start9 relay, but no longer run it.

I also already have a relay.tools relay at:
https://nortis.nostr1.com/

I'm now looking at the next level, a relay that I can fully control that runs from a server I control that costs me next to nothing and uses the  WoT model.

If it works on a RPi 4, but struggles to cope, I can upgrade to a RPi 5 and I also have a 2TB SSD I can add.

I have a 1GB fibre Internet connection at the home I would locate it at, so plenty of bandwidth.