From the Lenovo article:
Without a doubt, the biggest limitation of these systems, if you are going to use them as Proxmox hosts, is that they only have a single 1GB Ethernet adapters. There’s no upgrade potential here that doesn’t involve soldering and 3D printing.
You can use the WiFi M2 slot underneath the SATA caddy for another NIC, i just did that! My m910q had a fitting cover at the back, for the p320 (with removed GPU) it’s currently just hanging out. Got “M.2 Key A+E/PCI-E 2,5G Gigabit Ethernet Netzwerk Lan Karte 1000Mbps RTL8125BG Chip” from eBay. Working great so far (just a week or so though).
No, but neither do comments unless someone replies… Like me in this case I guess :D