Honestly I wouldn't necessarily look at hardware for OpenWRT specifically. Instead find options that you like and then filter based on OpenWRT support.
Here are some questions to help guide you:
- What is your price point?
- What Wireless standard do you want? You probably should look at either Wifi 5 or 6.
- Do you want new or used?
- How much ram do you need? (If you are running extra services)
- What throughput are you looking for?
Also, I personally would suggest looking at a base router, switch and some access points instead of just one device. If you do not want to hard wire you can look at mesh. Also make sure to avoid Broadcom devices like the plague.