I didn't know this hadn't been done yet... I've had the SysKonnect 9822 and the 3Com 996T both working, but couldn't get the newer SysKonnect 9D21 working under either vanilla Red Hat or SME. The 3Com is a breeze, but it's got a strange performance quirk - it's actually *faster* plugged into a 32-bit PCI slot than a 64-bit one: go figure. (All this was done under SME 4.x, since it was before 5.x came out. The SysKonnect cards offer maximum performance, but they're all *really* fast.)
Unfortunately, I no longer have access to this equipment for testing purposes, so I can't tell you if it works with 5.x or not...