“The PC consumes about 48W of power when idle (only management network connected) by default without further tuning.”
A Swiss ISP announced 25 Gbit/s home fiber before his local exchange could even deliver it. So he built a router from PC parts ahead of time. The hard part wasn’t Linux. It was finding a consumer mainboard with enough PCIe lanes for two network cards. ISPs sell the speed and leave you to work out the hardware.