Ystebad

So after changing to the new NIC everything else works on the LAN when the unraid server is plugged in or not?
 
Definitely do not enable any VLANS that must makes more things that can go wrong.
 
If everything else is working except the unraid server:
 
You need to look at your MAC address of the server (or the new ethernet card if you’re using that).
 
Make sure that only 1 port from the computer is plugged in at a time.
 
Look in your router to see where that MAC address is assigned and see if it’s reserved or any other settings are applied.  See if you can ping that address from another device on the network.
 
Check your firewall rules to make sure no rules are being applied to that MAC address/IP
 
I dont run unifi routing so can’t help you with any specific settings.  
 
If you have the same problem where everything goes down on the network when you plug a single cable into the NIC in your unraid server then make sure you try other ports on your router.  If that fixes it then you’ve either got a bad port or you have a setting messed up (like an uplink or something).  If that doesn’t fix it then it would seem you’ve got something misconfigured in your router or switching.