Request for advice regarding system extension

Seems like the system is not sharing its pci-e resources properly. I guess this could be a kernel issue for this new chip or it could be the syba controller stepping on the network adapter. I doubt it is a driver for the syba chipset (it works in many other devices I have) or the realtek network driver. Does the board have a newer bios available? It would be interesting to try even newer kernels but there isn't an easy way to do that.

Quote from Sean

Maybe I figured something out. My network controller's id is "enp3s0", but in /etc/network/interfaces ist was "enp2s0" (probably because there was only one SATA adapter during installation).

Your network controller id will change if you change the slot a card is in OR possibly plugging a card in to a slot if it comes before the onboard network controller. You shouldn't be seeing config in /etc/network/interfaces. You should run omv-firstaid.

Quote from Sean

I changed /etc/network/interfaces, and at first glance, it seems to work.

You shouldn't change config files because OMV will overwrite them. Also, OMV uses netplan now

Quote from Sean

Do I have to worry that the file will be overwritten the next time I change the configuration and press "apply"?

Yes. That is how OMV treats almost every config file it touches.