[kaylynb]

OPN/pfSense have been mentioned.

Don't waste time with WiFi on the gateway itself as most WiFI chips you can buy are crippled in firmware for regulatory reasons. Just use a dedicated commercial AP hooked up directly or VLANed.

Once you get comfortable with something like pfSense I highly recommend switching to regular Free/OpenBSD, or Linux depending on what you're comfortable with. I find it much easier to manage a gateway with the entire configuration in version control than a GUI. There aren't that many services that a gateway needs to run.

If you feel like you'll miss pf on the *BSDs check out nftables on Linux. It's not as well documented but it's much less painful than iptables.

To loop this into the UPnP discussion: when you build your own gateway from scratch you have to add a UPnP daemon and configure it yourself, instead of forgetting to disable it and exposing poorly configured IOT stuff.