I bough old FUJITSU Desktop (ESPRIMO D757/E90+) its ~2017 has 4 pcie. I bough cheap 3 ethernet NICs and 1 wi-fi on a maketplace/bazar and installed openWRT. Actually I installed proxmox and openWRT in a VM so that I can use that computer for other networking stuff like AdGuard, Tailscale, etc… Btw if you do this be careful which wifi you buy, not everything is easy to setup on OpenWRT.