It is on version 4 since installation. (not upgraded from 3 or anything).
I didn't move the NIC, it's the onboard!
In my opinion, it's OMV's drawback. It should assign your network settings to 'any' or 'the first' available interface..
Even so, you could still get locked out if simply your onboard card dies. Then you add a pci, but OMV would probably see and configure the onboard first.
It's mandatory, in my opinion, for a web interface environment, to allow you to pre-configure a non existing network interface.
Anyway, the question remains, will I mess up OMV if I edit the file?
enp2s0 is only mentioned twice. Once for the main network configuration and once for the vpn configuration.
If yes, my only hope is to add a pci ethernet first, really HOPE that it will get named enp3s0 and select it from OMV web interface,
then power-off, remove the nic, put the graphics card and boot..