Hello. I am having a similar problem. I am running a Lenovo Thinkstation P520 with the Chelsio T520 CR NIC in Proxmox 8.3.0. The card is visible as a device when I run lspci but I am not able to see the card in Proxmox. I have another of the same NICs in my Truesnas Scale Electric Eel box but it was detected and was able to link with my switch (another P520). As far as I can see, the kernel version for Proxmox and Truenas Scale Electric Eel are different. But Proxmox has the newer kernel. Shouldn't proxmox support this card? I am trying to figure out how to proceed. Please help if you can.