>> What is the "standard Ethernet device of MorphOS"?

> sum_ethernet.device

I don't think this driver exists and I don't think there is such thing as a "standard Ethernet device". In case you mean the sungem_eth.device, this driver is for the specific Broadcom Ethernet controllers built into the MorphOS-supported PPC Macs. Apart from the fact that this driver is a closed-source PPC binary file (and even if compiled for m68k wouldn't necessarily work with any TCP/IP stack other than MorphOS NetStack), UAE would have to emulate one of the supported Broadcom Ethernet controllers, which of course it doesn't.

> A wrapper 68k to use MorphOS TCP-IP should be possible not ?

Yes, using the host system's TCP/IP stack with a specially built stub driver is what UAE does on the mainstream platforms. Someone would have to add this feature to the MorphOS version of E-UAE.