The OpenWRT table of hardware should point you in the right direction. Even if you end up not using OpenWRT, it gives a fair idea of hardware capable of running alternate operating systems, https://openwrt.org/toh/start
If you are going the OpenWRT route, also consider https://openwisp.org/
I suppose you could deploy OpenWISP in a container on your router if it has the capacity.
It is more akin to Ubiquiti’s Unifi I would say. Allows you to manage multiple OpenWRT devices centrally, or at least the common configuration elements.