Get a PoE switch. Get a Raspberry Pi 4 with a PoE HAT. Setup a VLAN for your ISP with the port to the modem unlabeled and a labelled port to the Pi. Setup one or more VLANs for your home network and label them on the same port to the Pi. Install OpenWRT and configure VLANs like real interfaces. Put a Ubiquiti AP on the home network VLAN. Profit!