A link to the card might be useful
I had the same issue - yes it's the B460 chipset. It is supported in latest Kernel but the OMV distro hasn't caught up yet.
I got around it by using a USB to Ethernet adapter during the install. Install as normal, then do updates so you get the latest kernel.
Plug ethernet cables into both the motherboard and USB adapter, go into network settings in OMV and you'll find the motherboard adapter is disabled. Enable it and note the IP address, then disable the USB - you'll lose connection on your login, just re-login on the new IP address and you're good.
Yes, I was originally planning on using the DS380 and only having 8 bays, but mini-itx motherboards where quite expensive compared to the micro-atx at the time so I went for the bigger case.
The extra 2 bays will probably not needed for quite a while but when my order went in the caddies were on sale for $18 AUD each so I just added to cart!
I have previously outgrown a Netgear RN102 (4TB total), and then a QNAP TS431P (12TB total) so decided this would be an epic build that will last a long time with possible upgrades along the way.
I was always going to be PC based for something of this size, so first decision was the case. After a fair bit if research I settled on this. 8 bays natively, but hot swap caddies for the 5.25 bays are inexpensive so I have 10 hot swappable 3.5in bays.
Motherboard is nothing too fancy, MSI B460M Mortar (6 Sata ports, but you lose 1 for the M.2 SSD)
10th Gen Intel i3 processor
120GB SSD to host the OS
500GB M.2 SSD to use for Docker apps
Extra SATA ports were added with this card to give a total of 11 SATA + 1 M.2
I currently only have 6 of the 3.5 HDD bays populated with 4TB WD Reds, this meets current storage needs but gives plenty of room for expansion
I'm doing a DIY build now, have ordered and waiting arrival of one of these cases. It's 8 bays out of the box, but I have also ordered 2 5.25in caddies to give me a total of 10 hot swappable bays.