The most annoying thing that took most of the day to figure out was from the box my ISP provides. It's meant to act as the router. I had my own, but there wasn't a simple bridge mode but instead multiple settings to disable. One thing you needed to do was spoof the router's WAN port MAC address. Since I changed routers that changed, too. I was pulling my nonexistent hair out trying to figure that out until something clicked and I remembered that thing I did once a year ago :/