Ok sorry its been a busy day but here are the things I ordered and all work:

This one adds two ports, uses the M keyed slot, top right. I do not recommend this one because there is no way to mount the ports. You’ll have to zip tie it like I did. Very sloppy.

This one is what I’d recommend, it will take full use of that 1xPCIe 3.0 lane and fits the A+E slot. The RJ45 will screw nicely into the back of the chassis. FYI this is not EXACTLY what I bought but looks pretty much the same. If you want to use this with pfsense you might consider an Intel based chipset but i used Realtek fine on my setup.

Godspeed!

I’m in a rush but ive put Ethernet cards in both slots of my optiplex 3080 m.2 slots. The top right slot is vanilla and 4xpcie lanes,full speed. The bottom left is A+e keying and only 1x lane which is enough for 2.5gig Ethernet. This is ultimately what i used. For my prfesene box I added a second card, a 2 port Ethernet card to the top right m.2 slot and made it a four port beast.