Hmm, is it possible to skip the Ethernet adapters in a configuration of USBC-Eth-Eth-USBC and connect USBCs directly one to another?

Unfortunately, USB does not work like Firewire, where this was possible.

USB 4, i.e. Thunderbolt, allows the emulation of network interfaces if you interconnect the USB Type C ports with a cable, but here you have USB 3, so this does not work.

On USB 3 you could interconnect 2 ports only if one of them implemented the On-the-Go specification, so it could work as either a peripheral port or a host port. Here this also does not work. On a system where this had been allowed by the hardware, it is likely that you would have needed to write yourself a device driver that emulates a network interface, because I am not aware of an already existing one, unlike for USB 4.