Dual-band WiFi extender with different subnets

Hi everyone,

I have an OpenWRT dual-band router and I'd like to share the internet wirelessly in a separate subnet using it. I want to connect to the primary AP that is in 192.168.0.x/24 using the 2.4Ghz interface and share the internet on the 5Ghz interface in a different subnet with a different SSID (192.168.2.x/24), to have a dedicated network with internet access. I couldn't find a clear tutorial and most of them are related to single-band routers. I read something about the Relays, but it was not explained in detail.

I prefer using the web GUI interface to have a better understanding.

Please help me how can I figure it out. Thanks for your help.

I did something similar. See here.
I have a guestnet and main network routed via two vlans, but bands serve both networks. If you only have a single router you do not need to make the two vlans. In your case just make a duplicate for the "lan" interface. Bridge one band to one interface and the other band to the other interface. Add a separate firewall zone to set forwarding between the two subnets. etc