QUANTUM USB LAN CARD
Hi, My device Mac Pro doesn't recognise Quantum usb lan card in Big Sur
There are different models of Quantum USB lan card. You probably need an updated driver for it.
Secondly, USB is very power specific. If it is a USB-C based card, or connected to a USB-C adapter, make sure the adapter has its own power charging it directly. When you say you have a Mac Pro, is that a tower, or a notebook MacBook Pro? The notebooks that come with USB-C have their owner powercord that can either go through one of these two adapters to ensure power power, and there is a built-in ethernet port on these adapters:
https://www.smklink.com/products/usb-c-multi-port-hub
https://www.siig.com/catalogsearch/result/?q=JU-DK0F11-S1
For desktops they have built-in ethernet ports in the back, which if broke, you can often add a PCI card that is supported by them to add support. IF you are talking the newer cheesegrater model. The black "trash-can" model there are Thunderbolt-2 ethernet adapters which work better than USB for ethernet connectivity.
Big Sur is not supported on the older Mac Pro desktops.