I configured AP+STA for me thanks to this Wiki page https://openwrt.org/docs/guide-user/network/wifi/ap_sta. I actually did it through the web and at the end I kept DNS rebind protection enabled as I couldn't figure out why it should be disabled. Is it really necessary to disable the protection for some reason?
I'm not an expert on the subject but based on the knowledge I have I didn't understand why the protection would be harmful in this situation.