Pi4 but any other mini computer will do. I'm still unable to zap you, BTW.
Discussion
Dang. Well I no longer see the error when I click on my own zap button so maybe my update just hasn't propagated to your relays.
I still don't see your zap button (nor your profile pic) but this could be due to relays or whatever.
Do you have recommended paid relays?
No matter if you use free or paid, more important is how fast they are, IMHO.
Have a look at this site: https://nostr.watch/relays/find