The RTL8125 is a Realtek 2.5 Gbps chipset. I believe ASRock and MSI have put it on some Intel mainboards.
I know there are mainboards with ACQ-107 chipset (5 Gbps), but 2.5 is enough for me. I got some used 10 Gbps ethernet cards as a test, and they were expensive overkill for my application.
A PCIE card with RT8125 is pretty hard to find. I have only seen it listed wholesale (minimum quantity 200).
I guess the takeup of fast ethernet is going to be slow - the "prosumer" is just a niche market.