Do yourself a favour. Get a dedicated WiFi unit. Something like a TPLink EAP or a Ubiquiti AC Lite. Most consumer routers are crap for wifi (aka the ones the ISPs hand out) Use a dedicated WiFi unit and stop the hassles. Hardwire it back to the switch and enjoy the stability.
Something like this https://forum.openwrt.org/t/nanopi-r4s-rk3399-4g-is-a-great-new-openwrt-device is a decent router for up to 1Gb. Sadly its only currently supported in Snapshot. Hopefully when 21.02 is released properly this will be fixed.
Otherwise @frollic 's thread is a good start for suggestions and advice.