Comment by mwpmaybe

I've started buying Intel E810s for most purposes, even for 10G links. (SFP28 ports are generally backward-compatible with SFP+ DACs and transceivers.) The ones you can get on eBay for cheap typically run Dell firmware but it's serviceable. An E810-XXVDA2 is Gen4 x8; as long as the host slot can physically accept the card connector you only need Gen4 x1 electrical for a single 10G link or Gen4 x2 for dual 10G or single 25G.