Using a Netgear R7800. I did a clean install of OpenWRT 19.7.4 and without any other changes, I changed the LAN IP address and after doing so, I cannot access the router via web.
I created a video of everything I did so that people can see there was nothing funny going on. The video has many fast forwards in it, and of course I didn't record during reboots etc. but I show all of the relevant information. The video also shows that when I change the IP back to the default, LUCI works just fine.
Is this a bug? Or is there something I'm missing here?
On your first attempt your browser tried connecting via HTTPS (1:57), which I believe isn't enabled by default for luci on any firmware image as of yet. On the second attempt (3:05) when you tried going back to 192.168.1.0/24, your browser connected via http and that worked.
If you need HTTPS, you have to remove luci and install luci-ssl instead.
That was it! For some reason though, I cant get Chrome to even attempt a port 80 connection, even if I manually type http://10.10.10.1 or if I type 10.10.10.1:80 doesn't matter. However, Safari was able to connect using http://10.10.10.1 so that was obviously the problem.