I have an Arris S33 Modem which works well. It only has one annoying quirk which it that it blocks access to the Admin page for all machines behind a router. If I plug a computer into the modem directly and go to 188.8.131.52 I can access the modem's admin page fine.
However once I put same computer behind the router, nothing. My old Netgear Modem has no issue with this, it is a known limitation of the Arris S33.
I can get it to work if I take a custom Wifi SSID such as "Modem Admin", bridge it to the wan, connect a computer to it, and then give it a manual IP of 192.168.100.5. But I don't want to have to do all of that.
I've got a pretty complex setup and understand networking decently well, but I cannot figure out how to expose this address to the rest of my network transparently to the modem so any machine can just hit 192.168.100.1 and get to the admin page.
https://openwrt.org/docs/guide-user/network/wan/access.modem.through.nat Tried this and it prevents me from accessing the internet. Turning the interface on kills internet access, turning it off restores it. I suspect the modem responds back on the wrong Interface.