When the MOD-ENC28J60 Uext module is connected to the Olimexino-328 the upload of any sketch mit Arduino 1.8.14 fails with:
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
Without the Uext the upload works fine. The ethernet works fine.
Is this intended?
This is expected. The same pins that are used for UEXT's SPI are used also for ISP programming. The MOD-ENC28J60 uses SPI. The ATmega328 chip has only one SPI.
Not much that can be done about it.