How can I configure the default gateway for the DHCP server?

I have a GL-AR150 that I want to use as a DHCP and DNS server, but not as a router. I have no trouble getting both functions to work when I connect my home network (sans any other DHCP server) to the LAN interface of the GL-AR150, but then I have a problem. DHCP clients receive a default gateway address equal to that of the GL-AR150, but I am not using it as a router. I wish to specify a different gateway, or the computers on my network don’t correctly route packets to the Internet. I know dnsmasq supports this, but I don’t see any configuration options in the web config (in Luci or otherwise) that allow this. Anyone know how I can configure dnsmasq directly or configure this?

FWIW I can get the whole setup working in a functional way by using the GL-AR150 as a router, but the performance cost isn’t worth it. My main router supports much better bandwidth, but doesn’t provide a DNS server without me changing the firmware to something custom (also with a performance hit).

Maybe you want to use it as AP mode? https://docs.gl-inet.com/en/3/setup/mini_router/more_settings/#network-mode

I found what I needed. Under a network (e.g. lan), under DHCP Server Advanced Options, there is an option for DHCP-Options. Settings this to 3,192.168.1.1 sets the gateway (in my case to 192.168.1.1).

Is 192.168.1.1 your main router’s gateway?

yes

my issue is resolved