Router for 5GHz wireless WAN + 2.4GHz IoT VLAN

Hello everyone,

​I am looking for a hardware recommendation to run OpenWrt for my IoT setup.
​The router must receive its internet connection via 5GHz wifi from a primary router located on the floor below. It needs to broadcast its own 2.4GHz wifi network for approximately 30+ govee bulbs. I want to remain flexible to potentially integrate other IoT devices in the future as well. The 2.4GHz signal needs to cover one floor with a radius of about 20 meters.

​I want to set up a dedicated IoT VLAN. All IoT devices should be strictly blocked from accessing the internet. Home Assistant will be running in this network and I need to ensure that both Home Assistant and my smartphone maintain full internet access. Furthermore my smartphone must be able to communicate with Home Assistant.

​Which current models offer the best stability for this setup? I would like to stay under a maximum of 50€ for the router but I am also open to buying a used device.

​Thanks in advance for your suggestions!
Robin

(https://toh.openwrt.org/) + CPU filter: "mt798"