Mesa modbus and pktUart

7i76eu_7i76x1_pktv2d.bin 

Would be the correct firmware

You will also need to update LinuxCNC to the lastest version
sine the hm2_modbus driver is quite new.

 

Thx.
Just out of curiosity…
Is there an overview what all those firmwares do / are meant for?

Or how could I have found that out myself?

Regards

For configurations with specific daughtercards, the daughtercard 
name is included in the file name and you can use the .pin file
to determine the content and pinout of the firmware, for example
the 7i76eu_7i76x1_pktv2d.pin file shows that the configuration
includes a V2 PktUART ( the TX and RX halves )