Cross post here to see if anyone knows a workaround or if it is a known issue: OpenWrt support for Linksys MX4200 - #2539 by rkboni
I am using the non-mesh NSS build from AgustinLorenzo and followed OneMarcFifty's video to set up a main router and a dump AP, both of them have a wifi network and an IoT network, while using Vlan to separate the traffic, I got the similar DHCP issue as the post above.