How to merge two networks in OpenWRT LuCI?

Question

Network administration

The situation is as follows:
- there is a router ("Main") that distributes wifi with the Internet, a wifi network: 192.168.1.*
- there is a router ("Second") with OpenWRT firmware, connected (as a client) to the wifi network of the Main router, also to this (Second) router is connected by an ethernet cable to a computer, network: 192.168.0.*;
- there is an Airport Express router connected to the Wi-Fi network of the Main Router and used to transmit sound from a computer to an analog amplifier using Airplay technology.
Problem: Apparently, due to the fact that Airport Express and the computer are on different subnets, the Mac OS installed on the computer does not see Airport Express, and therefore it is not possible to stream music.
Q: How do I set up an OpenWRT router so that the computer can see the Airport Express?
Moreover, I would not want to "expand" the network of the Main router with the Second wifi router, since, it seems, this can reduce the overall performance of the network - although this is probably a simpler solution, since in this case the computer will be in the subnet of the Main router.
I don't want to mess with the firmware config files, so it would be great to do everything through the LuCI interface.

Answer 1

Normally, you need to drag your devices into the same network. Everything else is a perversion, especially on a home network.
Connect a second router with a cable if you don't want to lose speed.
You can also try connecting a second router to the first one in transparent client mode wiki.openwrt.org/doc/recipes/atheroswds for example.