I installed one LSI 9260 card and one Intel 10Gb LAN card on 2026T-6RF+. They can be detected when installed separately, but Intel LAN card cannot be detected when installed both cards together. Do you have BIOS that can fix it?
Please go into BIOS => Advanced => PCI/PnP Configuration, and set PCIe Width to "Force x8/x8" if you want to install both cards.