I don't know if it's related to the fact it's a USB adpter, but it's stuck at half duplex.

I tried the stock driver, the RTL8168(b) drivers.

Same thing. Even tried setting the adapter in full duplex in my go file.

A 8125 based adapter in a PCI-E 3.0 slot works in full duplex.

Any ideas before I return the USB adapter?

Diagnostics attached...

soundwave-diagnostics-20250602-1710.zip

If you have some temporary nic, get the realtek plugin installed.

tried both plugins, no difference. Running out of ideas...

Just a quick thought. lsusb -v reports it's at Superspeed (5G). That adapter is USB 3.1 with a C to A dongle. The motherboard is not 3.1 but 3.0. That's about the only thing I could think of... I'll test on my windows machine wich has 3.1 ports and report back tomorrow.

Check your switch. Might be something manually set on the port connected. Swapping port and/or port settings verify. Unlikely, but test another cable if not too much trouble.

Unfortunately, it's not a managed switch, and cables are 3-feet cat5e which work perfectly with a PCI-E card. But tried it anyways, and no difference.

Thanks all. I went back to a PCI-E adapter, runs fine (2.5Gb full duplex, transfers are around 250MB/s both ways), I'll try to use the NVME adapter in an old DELL Inspiron running as my test IPcop machine.

Thank you all...