I've gotten my NAS with OMV 5 up and running with 4 drives (3+1 boot) on an old Dell Optiplex 390 that I got from work(the i5 config). I have tried twice now to expand my storage capacity with a pci-e sata expansion card from amazon, and twice now it hasn't worked.
It just flashes this screen showing the Marvell 88SE92XX Adapter for about a second (sorry it's blurry - I can't focus and take the picture in time):
After that it just flashes _ (underscore) in the top left endlessly, and doesn't boot into OMV (or linux mint 20.1 from a USB for that matter, it will boot into linux mint normally without the card. Have not tried windows). When I unplug the sata cables from it and just have the card in the slot, it boots to OMV fine. When I have it all plugged in and try to go into the bios, it goes through this process where it shows the above screen for a second, then goes and shows me a list of options, with booting from one of my four main drives through UEFI and then booting from one of the drives off the sata card listed under legacy boot, or going into the bios or diagnostics (so the card is at least detected at some point). When I go into the actual bios, it doesn't appear and it only shows me the option for enabling or disabling my 4 sata devices. I have tried turning virtualization on and off but it still doesn't work. Does anyone know what the issue is? I'm starting to think that either I'm getting VERY unlucky with my cards OR I need to boot into windows and maybe get it to recognize and then download a driver? OR that it is an optiplex issue and that it will only work with 4 drives.