I just bought 2 ASUS ZenWiFi AX6600 routers which are running the up-to-date stock firmware 3.0.0.4.386_46061 and are in access point mode. I have been able to get guest isolation (blocking access to the local network) working on the primary access point with ebtables -t broute -A BROUTING -i...
[Solution]
After writing this post I discovered my problem, but I thought i'd include it here for future users that have the same problem. The DROP rule on BROUTING was ignored if it was created after I connected to the network. I had to reconnect to the wireless network for the BROUTING rule to...