Some new server cases I got have network indicator LEDs at the front, which would come in quite handy given the server's location and usage. But I couldn't find NICs that have pin for connecting these LEDs - is this something that is only found on server mainboards? I don't want to start soldering jumpers to my NICs if there's a simpler way :-)
I have never seen a network adapter card that actually has pin-outs for external LEDs. Doesn't mean they don't exist, but I've never seen one (including many models of server-grade Intel cards, over many years).
In the cases where I have seen chassis that have network activity LEDs that function, they were server-grade chassis using server-grade boards, with platform specifics that provide the integrated (on the server board) NIC ports' status via a pin-out to the 'extended' front panel header (not just the usual HDD, Power, reset, sleep header pin-outs/headers that you normally see on desktop boards).
Even those wouldn't give front panel status for discrete NIC adapters (adapters plugged in via an expansion slot).
Your best bet may be to check with the chassis' manufacturer to find out which motherboards have been tested, or are intended to be used, with that specific chassis to have full functionality (like working front panel NIC LEDs).