pfSense

Intel's information for i225/6 based network cards states they both require pcie gen 3.1 for interface. This requires use of UEFI booting since legacy BIOS only supports hardware up to pcie 3.0. I believe pcie gen 3.1 has additional power-saving features over regular 3.0 that are utilized by UEFI. This potentially may also be causing issues for some virtualized instances of pfSense that still utilize BIOS based install instead of UEFI.

https://www.intel.com/content/www/us/en/products/details/ethernet/gigabit-network-adapters/i226-network-adapters/products.htm

https://www.intel.com/content/dam/doc/guide/pci-express3-phy-implementation-considerations-idf2009-presentation.pdf