What's better than eero and has OpenWRT?
Discussion
I have one of these running OpenWRT.
https://www.linksys.com/ca/dual-band-ax3200-wifi-6-router-e8450/E8450-CA.html
Though I guess it depends what you consider better. I liked that this one was supported with 802.11ax among cpu, wifi chip set, ram, and flash.
Put 'ax' in the heading filter under "WLAN 5.0GHz"
Haven’t tried it, but I’ve read that you can flash OpenWRT to a UniFi access point.
it appears some unifi routers are supported