Hi everyone!

Which firewall rules (if any) do I need to be able to log all syslog traffic from my Mikrotik on a server on my LAN?

That would go thru the "output" firewall chain. If you have nothing in this chain, then your golden. If you are putting rules in this chain however, then make sure you are allowing syslog traffic to your server. I would suspect however, that you probably have nothing in the chain.

Brian