Replacing my ISP router with a UniFi Cloud Gateway Max

So I recently upgraded my home internet to full fibre, after which I also decided to upgrade my router as there were some things I wanted to do with my network that my ISP-provided router wasn't capable of. I replaced my mesh system with a UniFi one a couple years ago, so it made sense to stick with the UniFi brand and go with one of their routers, so £250 later, I had a Cloud Gateway Max on its way to me. I figured this would be a straightforward process, but my god was I wrong! First attempt So I took a backup of my Cloud Key1 config and figured I could unplug that, plug in the Cloud Gateway, restore the config and be done. I assumed there would be a couple things I needed to tweak, but for the most part, it would be a simple 10 minute job. Fuck. No. You see, dear reader, in order to configure the Cloud Gateway you need an internet connection. No internet connection, no configuration. So by unplugging my ISP router -thus killing the internet to my entire house - I couldn't even get…