the nano comes in two basic versions, v2 and v3 , the pinouts are different ..
second, the 328p version -may- require the CH340 comm driver
The comm driver you need depends on whether you have the FTDI or the CH340 USB to serial chips; this is separate from the micro controller chip which can be 168P or 328P. Both types of boards I received had the CH340 USB to serial chip, I successfully installed that. The WAVGAT board apparently needs its own set of files in the Board Manager too; those files define everything about the board and are the reason you can use the Arduino IDE to program so many different types of boards. Before I downloaded and installed the board manager files, the baud rate I had to used in the serial monitor were 1/4th the baud rate set in the sketch code; afterwards they matched. Problem is, the WAVGAT board drivers seem to not include information necessary to work with the ENC library.
BTW, I was able to find a reference to the baud rate mismatch issue where a register setting in the ATmega can cause this; but I couldn't find any information about how to change it. There a tons of Arduino clones available and while you are right, they fall into two main version, I have learned that there are quite a few with subtle variations. I am trying to learn how to either avoid the odd balls or cope with them.
UPDATE: I found most of my issue. WAVGAT uses a Chinese clone of the ATmega 328P. The microcontroller is labeled AVGA328P. The genuine nano runs at 16mHz and the AVGA328P can run at 32mHz but comes set to 4mHz so when your sketch says Serial.Begin (38400) you need to use 1/4th that in the Serial Monitor, namely, 9600. There is a very long thread on the www.arduino.ru
about all the differences and how to cope with them. Since I don't know Russian I used Google translate to sort of read the posts but the moral of the story is...I need some new, fully compatible, nanos. I also discovered that the ENC28J60 I was testing with is fried. I pulled a new one out of my inventory, wired it up to a genuine UNO, uploaded one of the EtherCard examples, and it worked. Troubleshooting is always so much fun when you think you have one problem and you actually have two or more.