How to configure two interfaces (LAN and WLAN)?

[Jose]

Yes. One way to connect two different DHCP domains (ARP domains, really) is with a router.

 

[balanga]

Yes. One way to connect two different DHCP domains (ARP domains, really) is with a router.

I'll see if pfSense is able to provide a solution for me, although I don't know if I can setup the wifi interface as a WAN connection...

 

[LibreQuest]

You can apparently set up a virtual interface for multiple connections too.

https://man.freebsd.org/cgi/man.cgi?lagg(4)

 

[smithi]

I'll see if pfSense is able to provide a solution for me, although I don't know if I can setup the wifi interface as a WAN connection...

All that was missing was NAT, remember, to link two distinct networks. Did you understand that in the end?

pfSense will certainly setup NAT for host/s on inside network/s, as well as a solid firewall for the whole net if correctly configured, so that may well suit your needs.