Pls, check my feedbacks. You will find lot of projects, including CP.
(openwrt/dd-wrt + coova-chilli).
Also CP on mobile routers, used in public transportation.
I implemented CP on various TP-Links, ZBTs, mikrotiks, WD, Xiaomi, ubiquitis ....
Besides custom firmware for routers I also do the technical stuff on the backend server (freeradius, social login, DB for client info, remote access to the hotspots etc.)
My bid is proxy, until requirement specs settled.