Considering that China controls most of the NIC supply, I doubt they would be too concerned about implementing a GPU based backdoor.
I’m surprised that we still don’t have a cheap domestic Data Diode option. It is clear that only way to be secure is to never directly connect to internet.
If you're referring to Realtek, that's Taiwanese.
Reality is boring. There have been supply chain attacks that installed malicious firmware or replaced pin compatible chips. That's not surprising, that's boring and old news.