We have a 3000 sq ft, two-story house made of cement blocks with a concrete terraza separating the two floors. Most of the interior walls also made constructed with cement blocks. What router do you recommend that will allow one to flash the Express VPN software onto? Do I need to have one on each floor?
The ASUS ZenWiFi AX (XT8) does support Express vpn, there are some steps to be taken to make it work.
You would simply download the OpenVPN config file as shown here, then on the suggested ASUS ZenWiFi AX (XT8) you would then upload the previously generated OpenVPN config into the Wireless Mesh router GUI as shown here.