Wouldn't they provide you with a 20Gb compatible router? I was curious and cat8 LAN cables support 40Gb/s. They are 3x as expensive as Cat7, but with I'm just a few meters away from the router, so about 10-15€ and that's the cables done.
Ah... the PCI-e ethernet card is where it gets pricey 😮 250€ for 10Gb card.
Damn...
Although, I'd be future proof for sure. That kind of speed will probably be enough for 20 years or so.